Peptides (v.28, #12)
Editorial Board (CO2).
Phosphorylation-dependent structure of ATF4 peptides derived from a human ATF4 protein, a member of the family of transcription factors by Julien Pons; Nathalie Evrard-Todeschi; Gildas Bertho; Josyane Gharbi-Benarous; Richard Benarous; Jean-Pierre Girault (2253-2267).
ATF4 plays a crucial role in the cellular response to stress and the F-box protein β-TrCP, the receptor component of the SCF E3 ubiquitin ligase responsible for ATF4 degradation by the proteasome, binds to ATF4, and controls its stability. Association between the two proteins depends on ATF4 phosphorylation of serine residues 219 and 224 present in the context of DpSGXXXpS, which is similar but not identical to the DpSGXXpS motif found in most other substrates of β-TrCP. We used NMR spectroscopy to analyze the structure of the 23P-ATF4 peptide. The 3D structure of the ligand was determined on the basis of NOESY restraints that provide an hairpin loop structure. In contrast, no ordered structure was observed in the NMR experiments for the nonphosphorylated 23-ATF4 in solution. This structural study provides information, which could be used to study the β-TrCP receptor–ligand interaction in docking procedure. Docking studies showed that the binding epitope of the ligand, is represented by the DpSGIXXpSXE motif. 23P-ATF4 peptide fits the binding pocket of protein β-TrCP very well, considering that the DpSGIXXpSXE motif adopts an S-turning conformation contrary to the extended DpSGXXpS motif in the other known β-TrCP ligands.
Keywords: ATF4 protein; Phosphorylated peptide P-ATF4; P-ATF4; β-TrCP protein; STD-NMR; Restrained molecular dynamics; Docking; Binding fragment;
Improvement of lipoxygenase inhibition by octapeptides by Marloes Schurink; Willem J.H. van Berkel; Harry J. Wichers; Carmen G. Boeriu (2268-2275).
The β-casein-derived octapeptide RINKKIEK is a noncompetitive inhibitor of soybean lipoxygenase (LOX). To investigate the molecular determinants for the enzyme–peptide interaction, a peptide library containing substitutional analogs of RINKKIEK was prepared by SPOT synthesis and analyzed for interaction with fluorescent-labeled LOX. The positively charged amino acid residues in RINKKIEK appear to be essential for the LOX–peptide interaction. Replacement of the negatively charged glutamic acid by any other amino acid residue improves LOX binding. For both RINKKIPK and RINKKISK this increase in LOX binding is accompanied by a threefold increase in LOX inhibition.
Keywords: Inhibitors; Lipoxygenase; Peptides; Protein–protein interactions; SPOT synthesis;
A library of linear undecapeptides with bactericidal activity against phytopathogenic bacteria by Esther Badosa; Rafael Ferre; Marta Planas; Lidia Feliu; Emili Besalú; Jordi Cabrefiga; Eduard Bardají; Emilio Montesinos (2276-2285).
A 125-member library of synthetic linear undecapeptides was prepared based on a previously described peptide H-K1KLFKKILKF10L-NH2 (BP76) that inhibited in vitro growth of the plant pathogenic bacteria Erwinia amylovora, Xanthomonas axonopodis pv. vesicatoria, and Pseudomonas syringae pv. syringae at low micromolar concentrations. Peptides were designed using a combinatorial chemistry approach by incorporating amino acids possessing various degrees of hydrophobicity and hydrophilicity at positions 1 and 10 and by varying the N-terminus. Library screening for in vitro growth inhibition identified 27, 40 and 113 sequences with MIC values below 7.5 μM against E. amylovora, P. syringae and X. axonopodis, respectively. Cytotoxicity, bactericidal activity and stability towards protease degradation of the most active peptides were also determined. Seven peptides with a good balance between antibacterial and hemolytic activities were identified. Several analogues displayed a bactericidal effect and low susceptibility to protease degradation. The most promising peptides were tested in vivo by evaluating their preventive effect of inhibition of E. amylovora infection in detached apple and pear flowers. The peptide H-KKLFKKILKYL-NH2 (BP100) showed efficacies in flowers of 63–76% at 100 μM, being more potent than BP76 and only less effective than streptomycin, currently used for fire blight control.
Keywords: Antimicrobial peptides; Fire blight; Combinatorial chemistry; Linear peptides;
Anti-inflammatory effects of moxifloxacin and human β-defensin 2 association in human lung epithelial cell line (A549) stimulated with lipopolysaccharide by Giovanna Donnarumma; Iole Paoletti; Elisabetta Buommino; Maria Rosaria Iovene; Laura Tudisco; Valentina Cozza; Maria Antonietta Tufano (2286-2292).
Epithelia in the human airways, from the nasal aperture to the alveoli, are covered in a protective film of fluid containing a number of antimicrobial proteins. Defensins are single-chain, strongly cationic peptides and are one of the most extensively studied classes of antimicrobial peptides. Moxifloxacin (MXF) is a fluoroquinolone that acts against both Gram positive and Gram negative bacteria. In this study, we evaluated the effects of HBD2, MXF and the association MXF/HBD2 on some cytokines and on the ICAM-1 expression in LPS-stimulated A549 cells. Our results suggest that by lowering the epithelial cell-derived IL-1β, IL-6, IL-8 and ICAM-1 expression, the MXF/HBD2 association interferes with the multifunctional cytokine network evolving during inflammatory processes of the respiratory tract; this anti-inflammatory potential could be of great value in the treatment of inflammatory disorders.
Keywords: β-Defensin 2; Moxifloxacin; A549 cells;
The antimicrobial peptide Tachyplesin III coated alone and in combination with intraperitoneal piperacillin-tazobactam prevents ureteral stent Pseudomonas infection in a rat subcutaneous pouch model by Daniele Minardi; Roberto Ghiselli; Oscar Cirioni; Andrea Giacometti; Wojciech Kamysz; Fiorenza Orlando; Carmela Silvestri; Gianni Parri; Elzbieta Kamysz; Giorgio Scalise; Vittorio Saba; Muzzonigro Giovanni (2293-2298).
We investigated the efficacy of Tachyplesin III alone or combined with piperacillin-tazobactam (TZP) to prevent biofilm formation in vitro and in a rat model of Pseudomonas aeruginosa ureteral stent infection. We have observed that in vitro TZP, in presence of Tachyplesin III, showed minimal inhibitory concentrations (MIC)s twofold and minimal bactericidal concentrations (MBC)s eightfold lower. The in vivo study showed that rats that received intraperitoneal TZP showed the lowest bacterial numbers. Tachyplesin III combined with TZP showed efficacies higher than that of each single compound. Coating ureteral stents with Tachyplesin III is able to inhibit bacterial growth up to 1000 times.
Keywords: Peptides; Tachyplesin III; Ureteral stents; Bacterial adhesion; Urinary tract infections; Biofilm;
Inducible antibacterial response of scorpion venom gland by Bin Gao; Caihuan Tian; Shunyi Zhu (2299-2305).
Innate immunity is the first line defense of multicellular organisms that rapidly operates to limit aggression upon exposure to pathogen microorganisms. Although the existence of some antibacterial peptides in scorpion venoms suggests that venom gland could be protected by these effector molecules, antibacterial activity of venom itself has not been assessed. In this study, we reported the antibacterial activity of the venom of Chinese scorpion Buthus martensii. Protease K digestion test indicated that it is venom peptide/protein components, as key players, which are involved in such antibacterial response. As the first step toward studying molecular mechanism of scorpion venom gland immunity, we established an infection model which supports inducible antibacterial response of scorpion venom gland. A known B. martensii antibacterial peptide gene BmKb1 was up-regulated at the transcriptional level after venom gland was challenged, suggesting its key defense role. This is further strengthened by the presence of several immune response elements in the BmKb1 promoter region. Our work thus provides the first evidence supporting the role of venom antibacterial peptides (ABPs) in controlling scorpion venom gland infection and lays a basis for characterizing related components involved in regulation of scorpion venom gland ABP gene expression.
Keywords: Innate immunity; Buthus martensii; Antibacterial peptide; Inducible expression; Venom;
Molecular cloning and electrophysiological studies on the first K+ channel toxin (LmKTx8) derived from scorpion Lychas mucronatus by Wenlan Wu; Shijin Yin; Yibao Ma; Ying Liang Wu; Ruiming Zhao; Geliang Gan; Jiuping Ding; Zhijian Cao; Wenxin Li (2306-2312).
LmKTx8, the first toxic gene isolated from the venom of scorpion Lychas mucronatus by constructing cDNA library method, was expressed and characterized physiologically. The mature peptide has 40 residues including six conserved cysteines, and is classified as one of α-KTx11 subfamily. Using patch-clamp recording, the recombinant LmKTx8 (rLmKTx8) was used to test the effect on voltage-gated K+ channels (Kv1.3) stably expressed in COS7 cells and large conductance-Ca2+-activated K+ (BK) channels expressed in HEK293. The results of electrophysiological experiments showed that the rLmKTx8 was a potent inhibitor of Kv1.3 channels with an IC50 = 26.40 ± 1.62 nM, but 100 nM rLmKTx8 did not block the BK currents. LmKTx8 or its analogs might serve as a potential candidate for the development of new drugs for autoimmune diseases.
Keywords: LmKTx8; Lychas mucronatus; α-KTx; Kv1.3; BK;
Isolation and characterization of a T-superfamily conotoxin from Conus litteratus with targeting tetrodotoxin-sensitive sodium channels by Junliang Liu; Qifeng Wu; Canhui Pi; Yu Zhao; Maojun Zhou; Lei Wang; Shangwu Chen; Anlong Xu (2313-2319).
A T-1-conotoxin, lt5d, was purified and characterized from the venom of vermivorous hunting cone snails Conus litteratus. The complete amino acid sequence of lt5d (DCCPAKLLCCNP) has been determined by Edman degradation. With two disulfide bonds, the calculated average mass is 1274.57 Da, which is confirmed by MALDI-TOF mass spectrometry (average mass 1274.8778). Under whole cell patch-clamp mode, lt5d inhibits tetrodotoxin-sensitive sodium currents on adult rat dorsal root ganglion neurons, but has no effects on tetrodotoxin-resistant sodium currents. The inhibition of TTX-sensitive sodium currents by lt5d was found to be concentration-dependent with the IC50 value of 156.16 nM. Thus, this is the first T-superfamily conotoxin identified to block TTX-sensitive sodium channels.
Keywords: Conus litteratus; T-1-conotoxin; Dorsal root ganglion; Sodium channels;
Decoralin, a novel linear cationic α-helical peptide from the venom of the solitary eumenine wasp Oreumenes decoratus by Katsuhiro Konno; Marisa Rangel; Joacir Stolarz Oliveira; Marcia Perez dos Santos Cabrera; Renato Fontana; Izaura Yoshico Hirata; Izumi Hide; Yoshihiro Nakata; Kanami Mori; Marii Kawano; Hiroyuki Fuchino; Setsuko Sekita; João Ruggiero Neto (2320-2327).
A novel peptide, decoralin, was isolated from the venom of the solitary eumenine wasp Oreumenes decoratus. Its sequence, Ser-Leu-Leu-Ser-Leu-Ile-Arg-Lys-Leu-Ile-Thr, was determined by Edman degradation and corroborated by solid-phase synthesis. This sequence has the characteristic features of linear cationic α-helical peptides; rich in hydrophobic and basic amino acids with no disulfide bond, and accordingly, it can be predicted to adopt an amphipathic α-helix secondary structure. In fact, the CD spectra of decoralin in the presence of TFE or SDS showed a high α-helical conformation content. In a biological evaluation, decoralin exhibited a significant broad-spectrum antimicrobial activity, and moderate mast cell degranulation and leishmanicidal activities, but showed virtually no hemolytic activity. A synthetic analog with C-terminal amidation showed a much more potent activity in all the biological assays.
Keywords: Decoralin; Solitary wasp venom; Cationic linear α-helical peptide; Amphipathic α-helix structure; Antimicrobial and leishmanicidal activity;
Molecular and functional characterization of a new non-hemorrhagic metalloprotease from Bothrops jararacussu snake venom with antiplatelet activity by Silvana Marcussi; Carolina P. Bernardes; Norival A. Santos-Filho; Maurício V. Mazzi; Clayton Z. Oliveira; Luiz Fernando M. Izidoro; André L. Fuly; Angelo J. Magro; Antonio S.K. Braz; Marcos R.M. Fontes; José R. Giglio; Andreimar M. Soares (2328-2339).
BjussuMP-II is an acidic low molecular weight metalloprotease (Mr ∼ 24,000 and pI ∼ 6.5), isolated from Bothrops jararacussu snake venom. The chromatographic profile in RP-HPLC and its N-terminal sequence confirmed its high purity level. Its complete cDNA was obtained by RT-PCR and the 615 bp codified for a mature protein of 205 amino acid residues. The multiple alignment of its deduced amino acid sequence and those of other snake venom metalloproteases showed a high structural similarity, mainly among class P-I proteases. The molecular modeling analysis of BjussuMP-II showed also conserved structural features with other SVMPs. BjussuMP-II did not induce hemorrhage, myotoxicity and lethality, but displayed dose-dependent proteolytic activity on fibrinogen, collagen, fibrin, casein and gelatin, keeping stable at different pHs, temperatures and presence of several divalent ions. BjussuMP-II did not show any clotting or anticoagulant activity on human citrated plasma, in contrast to its inhibitory effects on platelet aggregation. The aspects broached, in this work, provide data on the relationship between structure and function, in order to better understand the effects elicited by snake venom metalloproteases.
Keywords: Metalloprotease; Fibrinogenase; Snake venom; Bothrops jararacussu; Biological activity; Antiplatelet activity; cDNA; Molecular model;
Endogenous heptapeptide Met-enkephalin-Gly-Tyr binds differentially to duplicate delta opioid receptors from zebrafish by Veronica Gonzalez-Nuñez; Geza Toth; Raquel E. Rodríguez (2340-2347).
Met-enkephalin-Gly-Tyr (MEGY) is an endogenous peptide that binds to opioid sites in zebrafish and in rat brain homogenates. The aim of this work is to characterize the binding profile of this opioid ligand on two duplicate delta receptors from zebrafish, ZFOR1 and ZFOR4. Our results show that, while ZFOR1 presents one single binding site for [3H]-MEGY (K D = 4.0 ± 0.4 nM), the experimental data from ZFOR4 fit better to the two-site binding model (K D1 = 0.8 ± 0.2 nM and K D2 = 30.2 ± 10.2 nM). Two other MEGY synthetic analogues, (D-Ala2)-MEGY and (D-Ala2, Val5)-MEGY were also prepared and tested, together with the original peptide MEGY and other opioid ligands, in competition binding assays. While these peptides presented K i values on the nanomolar range when using [3H]-MEGY as radioligand, these parameters were two orders higher in competition binding assays with the antagonist [3H]-diprenorphine. Functional [35S]GTPγS stimulation analysis has revealed that these two receptors can be activated by several opioid agonists. Our results prove that although the MEGY peptide acts as an agonist on ZFOR1 and ZFOR4, there are subtle pharmacological differences between these two delta opioid receptors from zebrafish.
Keywords: Met-enkephalin-Gly-Tyr; Peptide analogues; Delta opioid receptor; Radioligand binding; [35S]GTPγS; Zebrafish;
In vitro and in vivo degradation of Aβ peptide by peptidases coupled to erythrocytes by Yinxing Liu; Hanjun Guan; Tina L. Beckett; Maria Aparecida Juliano; Luiz Juliano; Eun Suk Song; K. Martin Chow; M. Paul Murphy; Louis B. Hersh (2348-2355).
It is generally believed that amyloid β peptides (Aβ) are the key mediators of Alzheimer's disease. Therapeutic interventions have been directed toward impairing the synthesis or accelerating the clearance of Aβ. An equilibrium between blood and brain Aβ exists mediated by carriers that transport Aβ across the blood–brain barrier. Passive immunotherapy has been shown to be effective in mouse models of AD, where the plasma borne antibody binds plasma Aβ causing an efflux of Aβ from the brain. As an alternative to passive immunotherapy we have considered the use of Aβ-degrading peptidases to lower plasma Aβ levels. Here we compare the ability of three Aβ-degrading peptidases to degrade Aβ. Biotinylated peptidases were coupled to the surface of biotinylated erythrocytes via streptavidin. These erythrocyte-bound peptidases degrade Aβ peptide in plasma. Thus, peptidases bound to or expressed on the surface of erythroid cells represent an alternative to passive immunotherapy.
Keywords: Peptidases; Amyloid beta peptide; Peripheral degradation; Erythrocytes;
Aging and photoperiod affect the daily rhythm pattern of atrial natriuretic peptide in the rat atrium by Hayet Soualmia; Yasmina Djeridane; Joëlle Eurin; Yvan Touitou (2356-2360).
This study investigates the release characteristics of atrial natriuretic peptide (ANP) from young (10 weeks) and old (22 months) rat atrium. Levels of ANP release from samples of atrium were studied by organ perifusion. Rats were exposed to light:dark (LD) cycles of 12:12 or 18:6 and sacrificed at different zeitgeber time (ZT) points: ZT0, ZT6, ZT8, ZT12, ZT16, and ZT19 for LD 12:12 or ZT0, ZT9, ZT16, ZT18, ZT20, and ZT 21.5 for LD 18:6. The heart was collected, and the right atrium was removed, weighed, and perifused with Krebs-bicarbonate buffer for 100 min, including a period of 50 min for stabilization of secretion rate. ANP concentrations released by atrium did not differ between the two age groups either under LD 12:12 or under LD 18:6, except at the light:dark transition under LD 12:12 conditions where ANP levels were significantly (P < 0.05) lower in young compared to old rats. ANP exhibited daily variations in concentrations under LD 12:12, with a peak during the beginning of photophase (ZT0) in young rats and a peak at the beginning of scotophase (ZT12) in old animals. These variations were strongly modified under LD 18:6, where the pattern of the release exhibited a peak during the light phase at ZT16 in both young and old rats. This strongly suggests that the atrial ANP rhythm is dependent on the environmental light:dark cycle. Moreover, the total ANP levels released by atria in old rats were significantly increased under LD 18:6 compared to standard LD 12:12. This observation strongly suggests that old animals are more sensitive to a photoperiodic change. In conclusion, our results show that ANP concentrations in the rat atrium exhibit daily variations which are significantly affected by the daylength (photoperiod) change in aged rats.
Keywords: Atrial natriuretic peptide; Aging; Photoperiod; Rat; Perifusion;
The role of hypothalamic peptide gene expression in alcohol self-administration behavior by Chris Pickering; Lotta Avesson; Sture Liljequist; Jonas Lindblom; Helgi B. Schiöth (2361-2371).
Self-administration of ethanol and food share many common features and Richter hypothesized that an increase in ethanol consumption would decrease feeding to balance the excess calories contained in the ethanol. Previously, we have shown that individual alcohol consumption correlates with neurotransmitter gene expression, especially in the prefrontal cortex. To test the hypothesis of Richter, we measured hypothalamic gene expression of receptors or neuropeptides of known relevance for the regulation of food intake using qPCR and correlated this to individual ethanol consumption in Wistar rats. For validation, gene expression was first correlated with body weight. We found a correlation of dynorphin, somatostatin, melanocortin-4 receptor and serotonin 5-HT2C with body weight and trends to correlation for CART, thus confirming the established role of the hypothalamus in the regulation of weight. For ethanol consumption, correlations were found for CRH receptors 1 and 2 and vasopressin while strong trends were observed for galanin receptor 1, orexin receptor 1, MCH and adrenoceptor α1B. Therefore, alcohol consumption does seem to involve several hypothalamic systems which also mediate feeding responses and suggests that the hypothalamus, together with the prefrontal cortex, may determine the ‘stopping point’ of an individual.
Keywords: Ethanol; Hypothalamus; CRH; Galanin; Orexin; qPCR; Functional genomics; Wistar rat; Individual;
Permeability of the blood–brain barrier to a novel satiety molecule nesfatin-1 by Tulin O. Price; Willis K. Samson; Michael L. Niehoff; William A. Banks (2372-2381).
Nesfatin-1 has recently been identified as a hypothalamic and brain stem peptide that regulates feeding behavior. Here, we determined the ability of nesfatin-1 to cross the blood–brain barrier (BBB) of mice. We used multiple-regression analysis to determine that radioactively labeled nesfatin-1 injected intravenously entered the brain. The entry rate (K i) of 131I-nesfatin-1 from blood-to-brain was 0.20 ± 0.02 μl/g min. This modest rate of entry was not inhibited by the administration of nonradioactive nesfatin-1, suggesting that BBB transport of nesfatin-1 into the brain is by a nonsaturable mechanism. High performance liquid chromatography (HPLC) and acid precipitation showed that most of the injected radiolabeled nesfatin-1 reached the brain as intact peptide, and capillary depletion with vascular washout revealed that 67% of 131I-nesfatin-1 crossed the BBB to reach the brain parenchyma. Efflux of labeled nesfatin-1 from brain back into blood was by way of bulk flow. These findings demonstrate that nesfatin-1 crosses the BBB in both the blood-to-brain and brain-to-blood directions by nonsaturable mechanisms.
Keywords: Nesfatin-1; Anorexigenic peptide; Blood–brain barrier; Unidirectional influx rate;
The fasting polypeptide FGF21 can enter brain from blood by Hung Hsuchou; Weihong Pan; Abba J. Kastin (2382-2386).
FGF21 recently has been proposed as a missing link in the biology of fasting, raising the question of whether it directly reaches the brain. We used multiple time-regression analysis to quantify the influx rate of this polypeptide across the blood–brain barrier (BBB), size-exclusion chromatography to examine degradation, capillary depletion to differentiate entry into brain parenchyma from retention in the microvasculature, and measurement of efflux rate to determine a possible confounding effect on measurement of entry. FGF21 was 94% intact in serum and 75% in brain 10 min after intravenous bolus delivery. Its influx rate was 0.23 ± 0.12 μl/g-min, nearly four times faster than that of the vascular marker albumin. At 10 min, about 0.5% of the administered FGF21 was present in a gram of brain tissue. Of this, 70% reached the parenchyma of the brain. Co-injection of excess FGF21 failed to inhibit the influx, showing a lack of saturation. Efflux, which occurred at the same rate as the bulk reabsorption of cerebrospinal fluid, also was not saturable. In summary, FGF21 shows significant, non-saturable, unidirectional influx across the BBB.
Keywords: FGF21; Blood–brain barrier; Metabolism;
Human melanocytes expressing MC1R variant alleles show impaired activation of multiple signaling pathways by Richard A. Newton; Donald W. Roberts; J. Helen Leonard; Richard A. Sturm (2387-2396).
Variant alleles of the human MC1R gene are strongly associated with red hair color, fair skin and poor tanning ability (RHC-trait). Recently, we demonstrated that melanocytes harboring RHC-associated alleles have markedly reduced surface expression and/or impaired G-protein coupling of the corresponding receptor protein. The consequences of such a deficit on MC1R-mediated signaling pathways have now been quantitatively evaluated utilizing strains of human primary melanocytes homozygous for RHC-associated variant alleles and comparing responses to wild-type strains. The ability of melanocortin peptides to increase transcription of cAMP-dependent pigmentation genes, including MITF and SLC45A2, was abrogated in melanocytes with RHC-associated variant alleles, an effect that may contribute to the RHC phenotype. Activation of the c-Fos transcription factor gene was also severely compromised, a finding of potential relevance for non-pigmentary roles of MC1R. We also confirmed p38 signaling as an MC1R-regulated pathway and identified a large synergistic interaction between UV irradiation and MC1R stimulation for the activation of p38. This synergism was impaired in melanocytes expressing RHC variants of MC1R which may be relevant for the poor tanning ability associated with individuals possessing these alleles.
Keywords: Melanocortin-1 receptor; Melanocyte; p38; cAMP; UV; Signaling;
Structure–function analysis of the antiangiogenic ATWLPPR peptide inhibiting VEGF165 binding to neuropilin-1 and molecular dynamics simulations of the ATWLPPR/neuropilin-1 complex by Anna Starzec; Patrick Ladam; Roger Vassy; Sabah Badache; Nadia Bouchemal; Alda Navaza; Catherine Hervé du Penhoat; Gérard Y. Perret (2397-2402).
Heptapeptide ATWLPPR (A7R), identified in our laboratory by screening a mutated phage library, was shown to bind specifically to neuropilin-1 (NRP-1) and then to selectively inhibit VEGF165 binding to this receptor. In vivo, treatment with A7R resulted in decreasing breast cancer angiogenesis and growth. The present work is focused on structural characterization of A7R. Analogs of the peptide, obtained by substitution of each amino acid with alanine (alanine-scanning) or by amino acid deletion, have been systematically assayed to determine the relative importance of the side chains of each residue with respect to the inhibitory effect of A7R on VEGF165 binding to NRP-1. We show here the importance of the C-terminal sequence LPPR and particularly the key role of C-terminal arginine. In solution, A7R displays significant secondary structure of the backbone adopting an extended conformation. However, the functional groups of arginine are very flexible in the absence of NRP-1 pointing to an induced fit upon binding to the receptor. A MD trajectory of the A7R/NRP-1 complex in explicit water, based on the recent tuftsin/NRP-1 crystal structure, has revealed the hydrogen-bonding network that contributes to A7R's binding activity.
Cryptides: Buried secrets in proteins by Daniel C. Pimenta; Ivo Lebrun (2403-2410).
The proteome originally described the entire set of proteins expressed by a genome, tissue or organism. Subsequently this term was limited to all the expressed proteins at a given time under defined conditions. Hence, specializations such as functional proteome, cancer proteome, liver proteome and so forth have arisen. One particular proteome that has been recently described is the cryptome, a unique subset of already known proteins that has the ability of generating bioactive peptides and proteins when submitted to proteolytic cleavage, rather than the classical processing pathways. This is an idea in agreement with the concept that evolution is not related to the amount of genes or putative proteins that could be secreted by an organism, but to the way these proteins are processed. These ‘new’ molecules may have related or increased properties when compared to the ‘original’ molecule or possess completely unrelated biological effects, thus increasing the array of biological roles that can be associated to one given protein (or gene). In this work, we review this recent concept and put it into the toxinology field as well, an area in which the diversity of functional molecules (and roles) is essential for the survival of a given organism.
Keywords: Cryptome; Proteome; Peptidome; Cryptides; Crypteins; Peptides;
From MIF-1 to endomorphin: The Tyr-MIF-1 family of peptides by Weihong Pan; Abba J. Kastin (2411-2434).
The Tyr-MIF-1 family of small peptides has served a prototypic role in the introduction of several novel concepts into the peptide field of research. MIF-1 (Pro-Leu-Gly-NH2) was the first hypothalamic peptide shown to act “up” on the brain, not just “down” on the pituitary. In several situations, including clinical depression, MIF-1 exhibits an inverted U-shaped dose–response relationship in which increasing doses can result in decreasing effects. This tripeptide also can antagonize opiate actions, and the first report of such activity also correctly predicted the discovery of other endogenous antiopiate peptides. The tetrapeptide Tyr-MIF-1 (Tyr-Pro-Leu-Gly-NH2) not only shows antiopiate activity, but also considerable selectivity for the mu-opiate binding site. Tyr-W-MIF-1 (Tyr-Pro-Trp-Gly-NH2) is an even more selective ligand for the mu receptor, leading to the discovery of two more Tyr-Pro tetrapeptides that have the highest specificity and affinity for this site. These are the endomorphins: endomorphin-1 is Tyr-Pro-Trp-Phe-NH2 and endomorphin-2 is Tyr-Pro-Phe-Phe-NH2. Tyr-MIF-1 proved, contrary to the then prevailing dogma, that peptides can be saturably transported across the blood–brain barrier by a quantifiable transport system. Unexpectedly, the Tyr-MIF-1 transporter is shared with Met-enkephalin. In the era in which it was doubtful whether a peripheral peptide could exert CNS effects, the Tyr-MIF-1 family of peptides also explicitly showed that they can exert more than one central action that persists longer than their half-lives in blood. These peptides clearly illustrate that the name of a peptide restricts neither its actions nor its conceptual implications.
Keywords: Peptide; Antiopiate; Depression; Metabolism; Blood–brain barrier; Opioid; Analgesia; Tyr-MIF-1; Endomorphin;
Endogenous opiates and behavior: 2006 by Richard J. Bodnar (2435-2513).
This paper is the 29th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning 30 years of research. It summarizes papers published during 2006 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular–biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurological disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).
Keywords: Endogenous opioids; Enkephalin; Endorphin; Dynorphin; Nociceptin; Endomorphin; Mu-opioid receptor; Delta-opioid receptor; Kappa-opioid receptor; ORL-1 opioid receptor;