Peptides (v.25, #2)


The scorpion venom peptides with no disulfide bridge are rarely identified and poorly characterized so far. Here, we report the identification and characterization of four novel disulfide-bridge-free venom peptides (BmKa1, BmKa2, BmKb1 and BmKn2) from Buthus martensii Kasch. BmKa1 and BmKa2 are very acidic and hydrophilic, showing no any similarity to other proteins, whereas BmKb1 and BmKn2 both are basic, α-helical peptide with an amidated C-terminus, showing a little homology with other peptides. Functional tests with synthetic peptide showed that BmKn2 has strong antimicrobial activity against both Gram-positive and Gram-negative bacteria, whereas BmKb1 has weak activity in inhibiting the growth of these bacteria.
Keywords: Amphipathic; Antibacterial; Acidic peptide; Venom peptide; Molecular evolution;

Molecular cloning and functional expression of the alpha-scorpion toxin BotIII: pivotal role of the C-terminal region for its interaction with voltage-dependent sodium channels by Khadija Benkhadir; Riadh Kharrat; Sandrine Cestèle; Amor Mosbah; Hervé Rochat; Mohamed El Ayeb; Habib Karoui (151-161).
Alpha scorpion toxins bind to receptor site 3 on voltage-dependent sodium channels and inhibit their inactivation. The α-scorpion toxin BotIII is the most toxic protein of Buthus occitanus tunetanus. Its sequence differs only by three amino acid residues from that of AahII, the most active α-toxin. Due to their high affinity and selectivity for mammalian sodium channels, BotIII and AahII represent powerful tools for studying the molecular determinants of specificity for voltage-dependent sodium channels. Sequence analysis of BotIII gene has revealed two exons separated by a 381-bp intron and a signal peptide of 19 amino acids. We succeeded in expressing BotIII in significantly higher amounts than AahII the only expressed strict alpha anti-mammalian scorpion toxin reported in the literature. We have also modified specific amino acid residues of BotIII. The recombinant and the natural toxins differ by the amidation of the C-terminal residue. Toxicity and binding experiments indicated: (a) the affinity of rBotIII-OH and rAahII-OH (rBotIII-OH with the 3 mutations R10V, V51L, N64H) for the voltage-dependent sodium channels is reduced compared to the natural toxins. This data revealed the important role of the C-terminal amidation for the biological activity of BotIII and AahII; (b) the single mutation N64H is responsible for the difference of toxicity and affinity between rBotIII-OH and rAahII-OH; (c) the addition of the sequence GR to rBotIII-OH leads to the loss of biological activity. This study is in agreement with the important role attributed to the C-terminal sequence of α-toxins in their interaction with sodium channels receptors.
Keywords: Scorpion; Recombinant toxin; Sodium channel; Toxicity; Pharmacology; Amidation;

Five trypsin inhibitors, with N-terminal sequences demonstrating homology to each other and exhibiting a molecular weight of 5100, 4800, 4400, 4100, and 3900, respectively, were isolated from Momordica cochinchinensis seeds with a protocol involving acid extraction, ion exchange chromatography on SP-Sepharose chromatography, and RP-HPLC on a C18 column. Specific inhibitory activity against trypsin was demonstrated by the trypsin isoinhibitors with K i values ranging from 5.3×10−8 to 1.8×10−6  M. None of the isoinhibitors could be cleaved by trypsin.
Keywords: Momordica cochinchinensis; Squash family trypsin isoinhibitors;

Napins are 1:1 disulfide-linked complexes of a smaller (ca. 4 kDa) subunit and a larger (ca. 10 kDa) subunit. The intent of the present study was to ascertain the production of napin by the seeds of a Brassica species that has not been examined previously, and also to explore new biological activities of the napin. A heterodimeric 11-kDa napin-like polypeptide has been isolated from Chinese white cabbage (Brassica chinensis cv dwarf) seeds with a protocol comprising ion exchange chromatography on DEAE–cellulose, affinity chromatography on Affi-gel blue gel, fast protein liquid chromatography (FPLC)-ion exchange chromatography on Mono S and FPLC-gel filtration on Superdex 75. The N-terminal sequence of the 7-kDa subunit manifests striking similarity to napin large chain, albumin and trypsin inhibitor. The N-terminal sequence of the 4-kDa subunit is homologous to napin large chain and an antimicrobial peptide. The napin-like polypeptide inhibited translation in the rabbit reticulocyte system with an IC50 of 18.5 nM. This translation-inhibitory activity was stable between pH 4 and 11, and between 10 and 40 °C. The polypeptide inhibited trypsin with a higher potency (IC50=8.5 μM) than it inhibited chymotrypsin (IC50=220 μM), but was devoid of ribonuclease and antifungal activities. It manifested antibacterial activity against Pseudomonas aeruginosia, Bacillus subtilis, Bacillus cereus, and Bacillus megaterium. The results revealed that the napin-like polypeptide from Chinese white cabbage seeds exhibited some potentially exploitable activities.
Keywords: Napin; Cabbage; Brassica chinensis; Seeds; Translation-inhibitory activity;

Lactoferrampin: a novel antimicrobial peptide in the N1-domain of bovine lactoferrin by Marieke I.A van der Kraan; Jasper Groenink; Kamran Nazmi; Enno C.I Veerman; Jan G.M Bolscher; Arie V Nieuw Amerongen (177-183).
The antimicrobial activity of bovine lactoferrin is attributed to lactoferricin, situated in the N1-domain. Based on common features of antimicrobial peptides, a second putative antimicrobial domain was identified in the N1-domain of lactoferrin, designated lactoferrampin. This novel peptide exhibited candidacidal activity, which was substantially higher than the activity of lactoferrin. Furthermore, lactoferrampin was active against Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa, but not against the fermenting bacteria Actinomyces naeslundii, Porphyromonas gingivalis, Streptococcus mutans and Streptococcus sanguis. Notably, lactoferrampin is located in the N1-domain in close proximity to lactoferricin, which plays a crucial role in membrane-mediated activities of lactoferrin.
Keywords: Antimicrobial peptide; Lactoferrin; Lactoferricin; Lactoferrampin; C. albicans; Gram-positive bacteria; Gram-negative bacteria;

A conserved heptapeptide sequence in the waterborne attractin pheromone stimulates mate attraction in Aplysia by Scott F Cummins; Amy E Nichols; Krishna Rajarathnam; Gregg T Nagle (185-189).
Mate attraction in the marine mollusk Aplysia involves long-distance waterborne chemical signaling via the release of the peptide pheromone attractin during egg laying. Aplysia californica attractin attracts conspecifics, reduces the latency to mating, and stimulates hermaphroditic mating. Four additional members of the Aplysia attractin family have recently been characterized from Aplysia brasiliana, Aplysia fasciata, Aplysia depilans, and Aplysia vaccaria. The five sequences differ significantly, but share six cysteine residues and the strictly conserved sequence Ile30-Glu-Glu-Cys-Lys-Thr-Ser36. Attractin is attractive to geographically and evolutionarily distant species, suggesting that the conserved heptapeptide region may be important for mate attraction. Consistent with this prediction, a synthetic constrained cyclic peptide that contains the conserved heptapeptide sequence is significantly attractive in T-maze bioassays. The attractins are the first family of waterborne peptide pheromones characterized in invertebrates and are unique in that family members are not species-specific pheromonal attractants.
Keywords: Aplysia; Attractin; Albumen gland; Pheromone;

Identification of peptides mimicking the ligands of proteins phosphorylated by protein kinase CK2 by Elena Cardellini; Franco Felici; Gian Luigi Gianfranceschi (191-197).
Synthetic peptides containing a phosphorylation site for protein kinase CK2 were used to investigate their binding properties to other peptides/proteins. The aim of this work was to find an efficient procedure to search for these peptide/protein ligands. The goal was successfully achieved through screening of random peptide libraries displayed on phage. Peptides corresponding to the amino terminal region of topoisomerase I were synthesized in both phosphorylated and unphosphorylated form and used to screen the libraries. Four of the selected sequences were also tested for their reactivity with synthetic peptides corresponding to the carboxy terminal region of the largest subunit of RNA polymerase II. The positive reaction detected supports the hypothesis that the isolated sequences may represent mimics of ligands of proteins phosphorylated by protein kinase CK2.
Keywords: Synthetic peptides; Phage libraries; Phosphorylation; Protein kinase CK2;

The peptides NKDIL and EPDIM, respectively derived from the 2nd and 4th domains of βig-h3, were fully active in mediating cell adhesion through interactions with α3β1 integrin [Biochem. Biophys. Res. Commun. 294 (2002) 940; J. Biol. Chem. 275 (2000) 30907]. Here, the conformational differences between NKDIL and EPDIM in water and in membrane environments were studied using CD spectroscopy, and their structures in sodium dodecylsulfate micelles were determined by NMR. The two peptides adopt β-turn structures like RGD peptides, and have more regular structures in micelles than in aqueous buffers. EPDIM shows a distorted type I β-turn for the PDIM segment in a membrane environment. The structure of NKDIL is similar with the standard type I′ β-turn, but shows large backbone flexibility even in a membrane environment. The conformational change of the 4th repeated domain of βig-h3 in micelle solutions suggests that the Asp-Ile motif of the 4th fas-1 domain (EPDIM) would be solvent-exposed and could interact with integrin α3β1 in a membrane environment. The present study provides a structural basis of βig-h3 function and information for the development of integrin-regulating drugs involving the wound healing protein.
Keywords: βig-h3; EPDIM; NKDIL; NMR; CD; Membrane-binding;

Dimerization of the immunosuppressive peptide fragment of HLA-DR molecule enhances its potency by Zbigniew Szewczuk; Monika Biernat; Marcin Dyba; Michał Zimecki (207-215).
Our previous studies revealed that the nonapeptide fragment of HLA-DR molecule, located in the β chain 164–172 with the VPRSGEVYT sequence, suppresses the immune responses. The sequence is located on the exposed molecule loop, therefore it may be involved in the interactions with other proteins. We suggested that the loop may serve as a functional epitope on the HLA class II surface for intermolecular binding, and that possible mechanism of biological action of the synthesized peptides is associated with interfering of adhesion of HLA class II molecules to their coreceptors. It has been postulated that oligomerization of the coreceptors is required for stable binding to class II HLA. Based on the crystal dimeric structure of HLA-DR molecules, we designed, and synthesized molecules able to induce the putative coreceptors dimerization. The synthesized series of compounds consisted of two VPRSGEVYT sequences linked through their C-termini by spacers of different length: (VPRSGEVYTG n )2K-NH2 (n=4–6). The results demonstrate that the dimerization of the nonapeptide fragment of HLA-DR results in enhanced immunosuppressory properties.
Keywords: Superdimer of MHC class II; MHC fragments; Dimeric analogs; Immunosuppressors; Linker length;

To compare both the peptide molecular self-aggregation and the interaction with membrane lipids of the Alzheimer’s amyloid β (Aβ)40, Aβ42 peptides, and the cytotoxic peptides human amylin and prion (106–126) peptides, we applied a liposome aggregation technology. The kinetics of the changes in the optical density (ΔOD) of liposome suspensions generated by the aggregation of liposomes induced by these peptides, allowed us to comparatively analyze their phospholipid affinity and self-aggregation. The kinetic curves showed an initial nonlinear region where d(ΔOD)/dt followed first order kinetics corresponding to the binding of the peptides to the membrane of the liposome, a linear region where d(ΔOD)/dt was constant, corresponding to the interaction between two membrane-bound peptide molecules, and a final slower increasing nonlinear region that corresponds to nucleation or seeding of aggregation. The analysis of the aggregation curves demonstrated that amylin and prion peptides also showed affinity for the acidic phospholipid phosphatidylserine (PS), as it has previously been shown for the Alzheimer’s Aβ40, Aβ42 peptides. Aβ42 showed the highest, and amylin the lowest, affinity for the liposome membrane. When bound to the membrane of the liposomes, all the peptides preserved the self-aggregation characteristics observed in solution. Aging the Aβ40 and Aβ42 peptide solutions that permit molecular self-aggregation reduced their capacity to induce liposome aggregation. The self-aggregation of membrane-bound prion molecules was several orders of magnitude higher than that observed for the other toxic peptides. Incorporation of the ganglioside GM1 into the membrane of liposomes enhanced the peptide-induced liposome aggregation. Kinetic analysis revealed that this enhancement was due to facilitation of the formation of bridges between membrane-bound peptide molecules, demonstrating that the peptide–membrane interaction and the peptide amyloidogenesis are independent functions performed at separate molecular regions.
Keywords: Beta amyloid; Aβ; Prion; Amylin; Toxic peptides; Phosphatidylserine; Liposome aggregation; Membrane interaction;

Norleucine1-Angiotensin IV alleviates mecamylamine-induced spatial memory deficits by Mikel L Olson; Emily A Olson; Jacob H Qualls; Jessica J Stratton; Joseph W Harding; John W Wright (233-241).
The brain angiotensin AT4 receptor subtype has been implicated in cognitive processing. We initially established that intracerebroventricular administration of the nAChR-antagonist mecamylamine (mec) interfered with spatial memory performance in male Sprague–Dawley rats. Next we demonstrated that mec-induced deficits in spatial memory were overcome by the AT4 receptor-agonist Norleucine1-Angiotensin IV (Nle1-Ang IV). Nle1-Ang IV could not, however, compensate for spatial learning impairments precipitated by both mec and the mAChR-antagonist scopolamine. These findings support the importance of the AT4 receptor in cognitive processing and suggest that the ability of Nle1-Ang IV to improve spatial memory deficiencies may be dependant upon the brain cholinergic system.
Keywords: Angiotensin IV; AT4 receptor; Nicotinic acetylcholine receptor; Muscarinic acetylcholine receptor; Mecamylamine; Scopolamine; Spatial memory; Alzheimer’s disease; Rat;

NMR probing of in silico identification of anti-HPV16 E7 mAb linear peptide epitope by Darja Kanduc; Francesco P. Fanizzi; Guglielmo Lucchese; Stefan Stevanovic; Animesh A. Sinha; Abraham Mittelman (243-250).
A proteomics-based approach was exploited in order to individuate peptide sequences having the immunogenic potential to evoke humoral response. The epitope search utilized two parameters: the similarity level of the peptide sequence to the host’s proteins, and the peptide capability to bind to the major histocompatibility complex class II molecules. By this approach, the human papillomavirus 16 E749–63 RAHYNIVTFCCKCDS peptide was individuated as the immunogenic epitope recognized by an anti-HPV16 E7 monoclonal antibody raised against the full-length viral oncoprotein. In this report, two-dimensional nuclear magnetic resonance spectroscopic experiments unequivocally probe the HPV16 E7 epitope individuation.
Keywords: Epitope mapping; Peptide immunodominance; Computational biology; Nonself discrimination; HPV16 E7 oncoprotein;

In vitro effects of SIKVAV retro and retro-enantio analogues on tumor metastatic events by Núria Almiñana; M.Rosa Grau-Oliete; Francesca Reig; M.Pilar Rivera-Fillat (251-259).
The SIKVAV peptide, located on the long arm of the laminin α1 chain, promotes cell adhesion, invasion and migration of tumor and endothelial cells, resulting in tumor growth, angiogenesis and metastasis. In this paper, we report the synthesis of the SIKVAV peptide and its retro (reverse l-amino acid order) and retro-enantio (reverse d-amino acid order) analogues and their effect on three critical steps in the metastatic process: cell–extracellular matrix protein (ECM) adhesion, cell migration and homotypic cell adhesion, using B16F10 melanoma cells. Results show that all peptides compete with laminin-1 cell attachment, but only SIKVAV induces peptide–cell adhesion. Retro analogue, but not retro-enantio, inhibits cell adhesion to SIKVAV, indicating that retro peptide recognizes the SIKVAV receptors while retro-enantio does not. Retro-enantio peptide is able to inhibit cell migration, by contrast of the SIKVAV chemoattractant activity. All three peptides reduce the homotypic cell adhesion in a dose-dependent manner, but retro-enantio sequence is the most effective reaching a 35% inhibition of controls at the higher concentration. These findings suggest that that both analogues of SIKVAV peptide, especially retro-enantio, may be considered as potential antimetastatic agents.
Keywords: SIKVAV; Retro-enantio peptides; Melanoma; Cell proliferation; Cell adhesion; Cell migration;

Tumor anorexia: effects on neuropeptide Y and monoamines in paraventricular nucleus by Michael M. Meguid; Eduardo J.B. Ramos; Alessandro Laviano; Madhu Varma; Tomoi Sato; Chung Chen; Yong Qi; Undurti N. Das (261-266).
Paraventricular (PVN) concentrations of neuropeptide Y (NPY), serotonin (5-HT) and dopamine (DA) in anorectic tumor-bearing (TB) rats were measured before and after tumor resection. At onset of anorexia in TB versus non-tumor bearing (NTB) Controls 5-HT increased from 12.19±0.49 pg/μg to 14.89±0.81 pg/μg (P<0.05) while DA and NPY decreased from 7.34±0.42 pg/μg to 4.97±0.56 pg/μg and 23.47±4.27 pg/μg to 13.64±1.44 pg/μg, respectively (P<0.05). After tumor resection, these neuromediators normalized when compared to sham-operated NTB rats. NTB pair-fed Controls were also studied. We conclude that the increased 5-HT and the decreased DA and NPY concentrations in PVN are associated with cancer anorexia and that the NPY food stimulatory effect is linked to serotoninergic and dopaminergic systems in hypothalamus.
Keywords: Anorexia; Tumor-bearing; Food intake; Hypothalamus; Serotonin; Dopamine; NPY;

Neuropeptide Y (NPY) enhances ATP-stimulated inositol phosphate (InsP) formation in bovine chromaffin cells through an unknown mechanism. Chromaffin cells were transduced with the carboxyl terminus of β-adrenergic receptor kinase 1 (βARK1CT), a Gβγ subunits scavenger, using a recombinant adenovirus system. The adenovirus also expresses a green fluorescent protein (GFP) which serves as an index of transduction. Flow cytometry showed that up to 80% of chromaffin cells were transduced by the virus. There was a direct correlation between the βARK1CT inhibition of the NPY enhancement of ATP-stimulated InsP formation and the percent of cells expressing GFP (r 2=0.9993). These results demonstrate that Gβγ subunits are required for the NPY enhancement of ATP-stimulated InsP formation in bovine chromaffin cells.
Keywords: Neuropeptide Y; ATP; Purinergic; Chromaffin cell; Cross-talk; Gbeta/gamma;

Hexanoylation of a VPAC2 receptor-preferring ligand markedly increased its selectivity and potency by Ingrid Langer; Françoise Gregoire; Ingrid Nachtergael; Philippe De Neef; Pascale Vertongen; Patrick Robberecht (275-278).
We synthesized a VIP analog that combines mutations that decrease the affinity for the VPAC1 receptor but maintain a high affinity for the VPAC2 receptor with an amino-terminal hexanoylation that increases the affinity for the VPAC2 receptor with a limited decrease in the affinity of the VPAC1 receptor. The resulting Hexanoyl[A19,K27,28]VIP had the expected properties of a high affinity for the VPAC2 receptor and a low affinity for the VPAC1 receptor and also a low affinity for the PAC1 and secretin receptors. With a 1000-fold preference for the VPAC2 receptor and a IC50 value of binding of 1 nM, this compound is the most potent and the most selective agonist presently described.

Regulation of ghrelin secretion during pregnancy and lactation in the rat: possible involvement of hypothalamus by Kazuhiko Shibata; Hiroshi Hosoda; Masayasu Kojima; Kenji Kangawa; Yasuo Makino; Ikuko Makino; Tatsuhiko Kawarabayashi; Kojiro Futagami; Yutaka Gomita (279-287).
We investigated the plasma concentration of ghrelin peptide during pregnancy and lactation in rats. Plasma ghrelin levels on days 10 and 15 of pregnancy were significantly lower than those of the non-pregnant rats. Thereafter, the plasma ghrelin levels on day 20 of pregnancy sharply increased to levels comparable with those in non-pregnant rats. Ghrelin peptide concentrations in the stomach did not change significantly during pregnancy. In the hypothalamus, ghrelin mRNA levels were significantly lower on day 15 of pregnancy than in the non-pregnant rats. Also, plasma ghrelin levels were significantly lower in lactating dams than non-lactating controls on days 3 and 8 of lactation. We examined the possible involvement of prolactin and oxytocin in the regulation of plasma ghrelin concentrations during lactation. Although plasma prolactin levels were decreased by the administration of bromocriptine, plasma ghrelin levels did not differ significantly between vehicle- and drug-treated lactating rats. Administration of haloperidol produced a marked increase in plasma prolactin levels as compared with the non-lactating controls. However, plasma ghrelin levels were not significantly different between vehicle- and drug-treated rats. Administration of an oxytocin antagonist into the lateral ventricle significantly inhibited the increase in the plasma oxytocin level induced by acute suckling. However, plasma ghrelin levels did not significantly between the groups. These observations indicated that the decrease in serum ghrelin is caused by a loss of the contribution of hypothalamic ghrelin. Furthermore, the present results suggested that the suckling stimulus itself, but the release of prolactin or oxytocin, is the factor most likely to be responsible for the suppression of ghrelin secretion during lactation.
Keywords: Ghrelin; Pregnancy; Lactation; Hypothalamus; Suckling; Stomach;

Estrogen modulates ghrelin expression in the female rat stomach by Maki Matsubara; Ichiro Sakata; Reiko Wada; Mami Yamazaki; Kinji Inoue; Takafumi Sakai (289-297).
Ghrelin was recently identified as an endogenous ligand for GH secretagogue receptor. In this study, we investigated the effects of ovariectomy on the numbers of ghrelin-immunopositive and -expressing cells, ghrelin mRNA levels, and plasma ghrelin concentrations in 4- and 9-week-old female rats. Three days after ovariectomy, the number of ghrelin cells and plasma ghrelin level significantly increased in both 4- and 9-week-old rats and the ghrelin mRNA level also increased in 4-week-old rats. These responses were reversed by 17β-estradiol replacement. We also found that ghrelin-immunopositive cells express estrogen receptor α. These results suggested that estrogen is involved in the regulation of ghrelin expression.
Keywords: Ghrelin; Female rat; Ovariectomy; Stomach; Estrogen; Estrogen receptor;

Change in CCK-8 response after diet-induced obesity and MC3/4-receptor blockade by P.C Chandler; P.K Wauford; K.D Oswald; C.R Maldonado; M.M Hagan (299-306).
Little is known regarding satiety effects of systemically administered cholecystokinin (CCK-8) in propensity or resistance to dietary-induced obesity (DIO), and of its effect under conditions of melanocortin-3/4R blockade. We found that CCK-8 exerted greater satiety effects in DIO-prone but not DIO-resistant rats, and this occurred only when the rats were placed on a high-fat (HF) diet, when DIO-prone rats failed to compensate for the greater energy density of the diet. CCK-8 also suppressed intake stimulated by melanocortin-3/4R antagonist, SHU9119, but only after 24 h of increased feeding. This suggests that under both of these conditions, responsiveness to CCK’s satiety effect is not so much affected by a HF diet or significant increases in body weight per se, but by a failure to rapidly limit food intake to that needed only for metabolic need. Identification of an early feeding mediator that is most strongly activated by a HF diet or by an acute challenge to energy homeostasis should provide an ideal anti-obesity target adjunct to CCK-8.
Keywords: Food intake; Satiety; Melanocortin; SHU9119; High fat diet; Cholecystokinin; Body weight; Leptin; MC4 antagonist;

Functional opioid pathways are necessary for hypocretin-1 (orexin-A)-induced feeding by Donald C. Sweet; Allen S. Levine; Catherine M. Kotz (307-314).
We investigated the interaction of the orexigenic neuropeptide, hypocretin-1 (Hcrt-1, also known as orexin-A), with endogenous opioids (also orexigenic neuropeptides). Rats were injected with naltrexone (NTX, nonspecific opioid antagonist) i.p., i.c.v., in the lateral hypothalamus (LH), and in the accumbens shell (AcbSh), and naloxone methiodide (nonspecific opioid antagonist unable to cross the blood brain barrier) was injected i.p. Rats were then injected with Hcrt-1 in the LH. Food intake was measured for up to 4 h thereafter. Rats were also pretreated with NTX in the LH, with Hcrt-1 injected in the AcbSh. NTX suppressed Hcrt-1-induced feeding only when injected i.p., i.c.v., and in the AcbSh. These studies reveal the necessity for functional central opioidergic pathways involving the AcbSh, but not the LH in Hcrt-1-induced feeding.
Keywords: Appetite; Orexins; Feeding studies; Obesity;