Amino Acids (v.46, #6)

The construction of an amino acid network for understanding protein structure and function by Wenying Yan; Jianhong Zhou; Maomin Sun; Jiajia Chen; Guang Hu; Bairong Shen (1419-1439).
Amino acid networks (AANs) are undirected networks consisting of amino acid residues and their interactions in three-dimensional protein structures. The analysis of AANs provides novel insight into protein science, and several common amino acid network properties have revealed diverse classes of proteins. In this review, we first summarize methods for the construction and characterization of AANs. We then compare software tools for the construction and analysis of AANs. Finally, we review the application of AANs for understanding protein structure and function, including the identification of functional residues, the prediction of protein folding, analyzing protein stability and protein–protein interactions, and for understanding communication within and between proteins.
Keywords: Amino acid network; Network properties; Software tools; Protein structure and function

Supraspinal metabotropic glutamate receptor subtype 8: a switch to turn off pain by Enza Palazzo; Vito de Novellis; Francesco Rossi; Sabatino Maione (1441-1448).
Glutamate is the main excitatory neurotransmitter in the central nervous system and as such controls the majority of synapses. Glutamatergic neurotransmission is mediated via ionotropic and metabotropic glutamate receptors (iGluRs and mGluRs). Signaling via mGluRs permits to finely tune, rather than turning on/off, the excitatory neurotransmission as the iGluRs do. Eight mGluRs (mGluR1-8) have been cloned so far, which have been divided into three groups based on sequence homology, pharmacological properties and second messenger signaling. mGluRs are widely expressed both on glia and neurons. On neurons they are located both at postsynaptic (group I) and presynaptic sites (group II and III). Group II and III mGluR stimulation reduces glutamate release, which can prove useful in pathological conditions characterized by elevated glutamatergic neurotransmission which include chronic pain. Indeed, mGluRs are widely distributed on pain neuraxis. The recent development of selective mGluR ligands has permitted investigating the individual role of each mGluR on pain control. The development of (S)-3,4-dicarboxyphenylglycine, a selective mGluR8 agonist, has revealed the mGluR8 role in inhibiting pain and its related affective consequences in chronic pain conditions. mGluR8 proved also to be overexpressed in pain controlling areas during pathological pain guaranteeing the availability of a switch for turning off abnormal pain. Thus, mGluR8 corresponds to an ideal target in designing novel analgesics. This review will focus on the novel insights into the mGluR8 role on pain control, with particular emphasis on the supraspinal descending pathway, an antinociceptive endogenous source, whose activation or disinhibition (via mGluR8) induces analgesia.
Keywords: Glutamate; Chronic pain; Metabotropic glutamate receptor 8; Antinociceptive descending pathway; DHPG

Nutritional balance of essential amino acids and carbohydrates of the adult worker honeybee depends on age by Pier P. Paoli; Dion Donley; Daniel Stabler; Anumodh Saseendranath; Susan W. Nicolson; Stephen J. Simpson; Geraldine A. Wright (1449-1458).
Dietary sources of essential amino acids (EAAs) are used for growth, somatic maintenance and reproduction. Eusocial insect workers such as honeybees are sterile, and unlike other animals, their nutritional needs should be largely dictated by somatic demands that arise from their role within the colony. Here, we investigated the extent to which the dietary requirements of adult worker honeybees for EAAs and carbohydrates are affected by behavioural caste using the Geometric Framework for nutrition. The nutritional optimum, or intake target (IT), was determined by confining cohorts of 20 young bees or foragers to liquid diets composed of specific proportions of EAAs and sucrose. The IT of young, queenless bees shifted from a proportion of EAAs-to-carbohydrates (EAA:C) of 1:50 towards 1:75 over a 2-week period, accompanied by a reduced lifespan on diets high in EAAs. Foragers required a diet high in carbohydrates (1:250) and also had low survival on diets high in EAA. Workers exposed to queen mandibular pheromone lived longer on diets high in EAA, even when those diets contained 5× their dietary requirements. Our data show that worker honeybees prioritize their intake of carbohydrates over dietary EAAs, even when overeating EAAs to obtain sufficient carbohydrates results in a shorter lifespan. Thus, our data demonstrate that even when young bees are not nursing brood and foragers are not flying, their nutritional needs shift towards a diet largely composed of carbohydrates when they make the transition from within-hive duties to foraging.
Keywords: Honeybee; Amino acid; Nutrition; Protein-to-carbohydrate ratio; Apis mellifera ; Diet

Phosphorylation is one of the most essential post-translational modifications in eukaryotes. Studies on kinases and their substrates are important for understanding cellular signaling networks. Because of the cost in time and labor associated with large-scale wet-bench experiments, computational prediction of phosphorylation sites becomes important and many computational tools have been developed in the recent decades. The prediction tools can be grouped into two categories: kinase-specific and non-kinase-specific tools. With more kinases being discovered by the new sequencing technologies, accurate non-kinase-specific prediction tools are highly desirable for whole-genome annotation in a wider variety of species. In this manuscript, a support vector machine is used to combine eight different sequence level scoring functions to predict phosphorylation sites. The attributes used by this work, including Shannon entropy, relative entropy, predicted protein secondary structure, predicted protein disorder, solvent accessible area, overlapping properties, averaged cumulative hydrophobicity, and k-nearest neighbor, were able to obtain better results than the previously used attributes by other similar methods. This method achieved AUC values of 0.8405/0.8183/0.7383 for serine (S), threonine (T), and tyrosine (Y) phosphorylation sites, respectively, in animals with a tenfold cross-validation. The model trained by the animal phosphorylation sites was also applied to a plant phosphorylation site dataset as an independent test. The AUC values for the independent test dataset were 0.7761/0.6652/0.5958 for S/T/Y phosphorylation sites, which compared favorably with those of several existing methods. A web server based on our method was constructed for public use. The server, trained model, and all datasets used in the current study are available at http://sysbio.unl.edu/PhosphoSVM .
Keywords: Phosphorylation site prediction; Non-kinase-specific tool; Support vector machine

Bleomycin hydrolase and hyperhomocysteinemia modulate the expression of mouse proteins involved in liver homeostasis by Joanna Suszyńska-Zajczyk; Jacek Wróblewski; Olga Utyro; Magdalena Łuczak; Łukasz Marczak; Hieronim Jakubowski (1471-1480).
The liver is the major contributor to homocysteine (Hcy) metabolism and fatty liver disease is associated with hyperhomocysteinemia. Bleomycin hydrolase (Blmh) is an aminohydrolase that also participates in Hcy metabolism by hydrolyzing Hcy-thiolactone. To gain insight into hepatic functions of Blmh, we analyzed the liver proteome of Blmh −/− and Blmh +/+ mice in the absence and presence of diet-induced (high methionine) hyperhomocysteinemia using 2D IEF/SDS-PAGE gel electrophoresis and MALDI–TOF mass spectrometry. We identified eleven liver proteins whose expression was significantly altered as a result of the Blmh gene inactivation. The differential expression (Blmh −/− vs. Blmh +/+) of four liver proteins was lower, of two proteins was higher, and was further modified in mice fed with a hyperhomocysteinemic high-Met diet. The down-regulated proteins are involved in lipoprotein metabolism (ApoA1, ApoE), antigen processing (Psme1), energy metabolism (Atp5h, Gamt), methylglyoxal detoxification (Glo1), oxidative stress response (Sod1), and inactivation of catecholamine neurotransmitters (Comt). The two up-regulated proteins are involved in nitric oxide generation (Ddah1) and xenobiotic detoxification (Sult1c1). We also found that livers of Blmh −/− mice expressed a novel variant of glyoxalase domain-containing protein 4 (Glod4) by a post-transcriptional mechanism. Our findings suggest that Blmh interacts with diverse cellular processes—from lipoprotein metabolism, nitric oxide regulation, antigen processing, and energy metabolism to detoxification and antioxidant defenses—that are essential for liver homeostasis and that modulation of these interactions by hyperhomocysteinemia underlies the involvement of Hcy in fatty liver disease.
Keywords: Bleomycin hydrolase; High methionine diet; Hyperhomocysteinemia; Mouse liver proteome

A new 68Ga-labeled BBN peptide with a hydrophilic linker for GRPR-targeted tumor imaging by Donghui Pan; Yu Ping Xu; Rong Hua Yang; Lizhen Wang; Fei Chen; Shineng Luo; Min Yang; Yongjun Yan (1481-1489).
Bombesin (BBN) is a peptide exhibiting high affinity for the gastrin-releasing peptide receptor (GRPR), which is overexpressed on several types of cancers. Various GRPR antagonists and agonists have been labeled with radiometals for positron emission tomography (PET) imaging of GRPR-positive tumors. However, unfavorable hepatobiliary excretion such as high intestinal activity may prohibit their clinical utility for imaging abdominal cancer. In this study, the modified BBN peptide with a new hydrophilic linker was labeled with 68Ga for PET imaging of GRPR-expressing PC-3 prostate cancer xenograft model. GRPR antagonists, MATBBN (Gly-Gly-Gly-Arg-Asp-Asn-d-Phe-Gln-Trp-Ala-Val-Gly-His-Leu-NHCH2CH3) and ATBBN (d-Phe-Gln-Trp-Ala-Val-Gly-His-Leu-NHCH2CH3), were conjugated with 1,4,7-triazacyclononanetriacetic acid (NOTA) and labeled with 68Ga. Partition coefficient and in vitro stability were also determined. GRPR binding affinity of both tracers was investigated by competitive radioligand binding assay. The in vivo receptor targeting potential and pharmacokinetic of 68Ga-NOTA-MATBBN were also evaluated in PC-3 prostate tumor model and compared with those of 68Ga-NOTA-ATBBN. NOTA-conjugated BBN analogs were labeled with 68Ga within 20 min with a decay-corrected yield ranging from 90 to 95 % and a radiochemical purity of more than 98 %. The specific activity of 68Ga-NOTA-MATBBN and 68Ga-NOTA-ATBBN was at least 16.5 and 11.9 GBq/μmol, respectively. The radiotracers were stable in phosphate-buffered saline and human serum. 68Ga-NOTA-MATBBN was more hydrophilic than 68Ga-NOTA-ATBBN, as indicated by their log P values (−2.73 ± 0.02 vs. −1.20 ± 0.03). The IC50 values of NOTA-ATBBN and NOTA-MATBBN were similar (102.7 ± 1.18 and 124.6 ± 1.21 nM). The accumulation of 68Ga-labeled GRPR antagonists in the subcutaneous PC-3 tumors could be visualized via small animal PET. The tumors were clearly visible, and the tumor uptakes of 68Ga-NOTA-MATBBN and 68Ga-NOTA-ATBBN were determined to be 4.19 ± 0.32, 4.00 ± 0.41, 2.93 ± 0.35 and 4.70 ± 0.40, 4.10 ± 0.30, 3.14 ± 0.30 %ID/g at 30, 60, and 120 min, respectively. There was considerable accumulation and retention of 68Ga-NOTA-ATBBN in the liver and intestines. In contrast, the abdominal area does not have much retention of 68Ga-NOTA-MATBBN. Biodistribution data were in accordance with the PET results, showing that 68Ga-NOTA-MATBBN had more favorable pharmacokinetics and higher tumor to background ratios than those of 68Ga-NOTA-ATBBN. At 1 h postinjection, the tumor to liver and intestine of 68Ga-NOTA-MATBBN were 8.05 ± 0.56 and 21.72 ± 3.47 and the corresponding values of unmodified counterpart were 0.85 ± 0.23 and 3.45 ± 0.43, respectively. GRPR binding specificity was demonstrated by reduced tumor uptake of radiolabeled tracers after coinjection of an excess of unlabeled BBN peptides. 68Ga-NOTA-MATBBN exhibited GRPR-targeting properties both in vitro and in vivo. The favorable characterizations of 68Ga-NOTA-MATBBN such as convenient synthesis, specific GRPR targeting, high tumor uptake, and satisfactory pharmacokinetics warrant its further investigation for clinical cancer imaging.
Keywords: 68Ga; NOTA; MATBBN; Gastrin-releasing peptide receptor; Prostate tumor

Plasma and lymphocyte Hsp72 responses to exercise in athletes with prior exertional heat illness by Patricia A. Ruell; David Simar; Julien D. Périard; Stuart Best; Corinne Caillaud; Martin W. Thompson (1491-1499).
We investigated the effect of exercise in the heat on both intracellular and extracellular Hsp72 in athletes with a prior history of exertional heat illness (EHI). Two groups of runners, one consisting of athletes who had a previous history of EHI, and a control group (CON) of similar age (29.7 ± 1.2 and 29.1 ± 2 years CON vs. EHI) and fitness [maximal oxygen consumption $$(dot V{{ ext{O}}_2}hbox{max} )$$ ( V ˙ O 2 max ) 65.7 ± 2 and 64.5 ± 3 ml kg−1 min−1 CON vs. EHI] were recruited. Seven subjects in each group ran on a treadmill for 1 h at 72 % $$dot V{{ ext{O}}_2}hbox{max}$$ V ˙ O 2 max in warm conditions (30 °C, 40 % RH) reaching rectal temperatures of ~39.3 (CON) and ~39.2 °C (EHI). Blood was collected every 10 min during exercise and plasma was analysed for extracellular Hsp72. Intracellular Hsp72 levels were measured in both monocytes and lymphocytes before and immediately after the 60-min run, and then after 1 h recovery at an ambient temperature of 24 °C. Plasma Hsp72 increased from 1.18 ± 0.14 and 0.86 ± 0.08 ng/ml (CON vs. EHI) at rest to 4.56 ± 0.63 and 4.04 ± 0.45 ng/ml (CON vs. EHI, respectively) at the end of exercise (p < 0.001), with no difference between groups. Lymphocyte Hsp72 was lower in the EHI group at 60 min of exercise (p < 0.05), while monocyte Hsp72 was not different between groups. The results of the present study suggest that the plasma Hsp72 response to exercise in athletes with a prior history of EHI remained similar to that of the CON group, while the lymphocyte Hsp72 response was reduced.
Keywords: Heat stroke; Plasma Hsp72; Exercise; Peripheral blood mononuclear cells

Effects of β-hydroxy-β-methylbutyrate free acid and cold water immersion on post-exercise markers of muscle damage by Adam M. Gonzalez; Jeffrey R. Stout; Adam R. Jajtner; Jeremy R. Townsend; Adam J. Wells; Kyle S. Beyer; Carleigh H. Boone; Gabriel J. Pruna; Gerald T. Mangine; Tyler M. Scanlon; Jonathan D. Bohner; Leonardo P. Oliveira; Maren S. Fragala; Jay R. Hoffman (1501-1511).
The aim of the current study was to examine the effects of cold water immersion (CWI) with and without the free acid form of β-hydroxy-β-methylbutyrate (HMB-FA) on markers of muscle damage following acute lower body resistance exercise. Forty recreationally resistance-trained men (22.3 ± 2.4 years) were randomly divided into one of the four groups: (1) Placebo (PL); (2) HMB-FA; (3) HMB-FA-CWI; (4) PL-CWI. HMB-FA groups ingested 3 g day−1 and CWI groups submersed their lower body into 10–12 °C water for 10-min post-exercise. No differences between groups were observed for CK; however, PL-CWI had significantly greater elevations in myoglobin 30-min post-exercise compared to HMB-FA (p = 0.009) and PL (p = 0.005), and HMB-FA-CWI was significantly greater than HMB-FA (p = 0.046) and PL (p = 0.028). No differences between groups were observed for IL-6 and IL-10, although CRP was significantly greater 24-h post-exercise for PL-CWI compared to HMB-FA-CWI (p = 0.02) and HMB-FA (p = 0.046). Only HMB-FA-CWI showed significantly (p = 0.02) greater improvements in average power per repetition. CWI appeared to elevate myoglobin compared to other groups, while HMB-FA may have attenuated the increase in CRP when combined with CWI. Nevertheless, HMB-FA or CWI treatments did not appear to provide benefit over PL for recovery. Instead, the combination of CWI and HMB-FA improved performance recovery compared to other groups.
Keywords: Cytokines; C-reactive protein; Myoglobin; Recovery; HMB; Cryotherapy

Microtubule components α- and β-tubulin undergo a number of posttranslational modifications that modulate their dynamics and cellular functions. These modifications include polyamination and covalent crosslinking by transglutaminase enzymes. We have demonstrated previously that the less dynamic and more stable tubulin form—detyrosinated Glu-tubulin—is found in high molecular weight, oligomeric complexes in bone-forming osteoblasts during differentiation and along with deposition of collagenous extracellular matrix. In this study, we report that oligomeric Glu-tubulin has high nocodazole tolerance, indicating further increased stability. We show that α-tubulin, which gives rise to Glu-tubulin, is a transglutaminase substrate in in vitro assays and that it is crosslinked into oligomers (dimers, trimers and tetramers) by transglutaminase 2 and Factor XIIIA; β-tubulin was not crosslinked by transglutaminase activity. The oligomeric Glu-tubulin was specifically localized to the plasma membrane of osteoblasts as analyzed by subcellular fractionation, cell surface biotinylation experiments and total internal reflection fluorescence (TIRF) microscopy. Glu- and α-tubulin co-localized with cellular Factor XIIIA as analyzed by conventional and TIRF microscopy. The Factor XIIIA-specific substrate peptide bF11 co-localized with α-tubulin and acted as a competitive inhibitor to oligomerization of Glu-tubulin, attenuating its formation in cells. This was associated with significantly decreased type I collagen deposition and decreased secretory activity as measured by synaptotagmin VII levels on the osteoblast plasma membrane. Our results suggest that Glu-tubulin may exist as covalently stabilized form which may be linked to the secretion and elaboration of collagenous extracellular matrix.
Keywords: Glu-tubulin and detyrosinated tubulin; Covalent crosslinking; Factor XIIIA transglutaminase; Type I collagen secretion

Increased expression of transglutaminase 2 drives glycolytic metabolism in renal carcinoma cells by Bo Mi Ku; Chang-Hun Lee; Seon-Hyeong Lee; Soo-Youl Kim (1527-1536).
Transglutaminase 2 (TGase 2) expression and glycolysis are increased in most renal cell carcinoma (RCC) cell lines compared to the HEK293 kidney cell line. Although increased glycolysis and altered tricarboxylic acid cycle are common in RCC, the detailed mechanism by which this phenomenon occurs remains to be elucidated. In the present study, TGase 2 siRNA treatment lowered glucose consumption and lactate levels by about 20–30 % in RCC cells; conversely, high expression of TGase 2 increased glucose consumption and lactate production together with decreased mitochondrial aconitase (Aco 2) levels. In addition, TGase 2 siRNA increased mitochondrial membrane potential and ATP levels by about 20–30 % and restored Aco 2 levels in RCC cells. Similarly, Aco 2 levels and ATP production decreased significantly upon TGase 2 overexpression in HEK293 cells. Therefore, TGase 2 leads to depletion of Aco 2, which promotes glycolytic metabolism in RCC cells.
Keywords: Transglutaminase 2; Aconitase 2; Glycolysis; Renal cell carcinoma

Cerebral ischemic preconditioning reduces glutamate excitotoxicity by up-regulating the uptake activity of GLT-1 in rats by Jianxue Gong; Shujuan Gong; Min Zhang; Lianwei Zhang; Yuyan Hu; Yixian Liu; Wenbin Li (1537-1545).
Our previous study has shown that cerebral ischemic preconditioning (CIP) can up-regulate the expression of glial glutamate transporter-1 (GLT-1) during the induction of brain ischemic tolerance in rats. The present study was undertaken to further explore the uptake activity of GLT-1 in the process by observing the changes in the concentration of extracellular glutamate with cerebral microdialysis and high-performance liquid chromatography. The results showed that a significant pulse of glutamate concentration reached the peak value of sevenfold of the basal level after lethal ischemic insult, which was associated with delayed neuronal death in the CA1 hippocampus. When the rats were pretreated 2 days before the lethal ischemic insult with CIP which protected the pyramidal neurons against delayed neuronal death, the peak value of glutamate concentration decreased to 3.9 fold of the basal level. Furthermore, pre-administration of dihydrokainate, an inhibitor of GLT-1, prevented the protective effect of CIP on ischemia-induced CA1 cell death. At the same time, compared with the CIP + Ischemia group, the peak value of glutamate concentration significantly increased and reached sixfold of the basal level. These results indicate that CIP induced brain ischemic tolerance via up-regulating GLT-1 uptake activity for glutamate and then decreasing the excitotoxicity of glutamate.
Keywords: Cerebral ischemic preconditioning; GLT-1; Glutamate; Microdialysis; HPLC; Dihydrokainate

Near-infrared fluorescence imaging of CD13 receptor expression using a novel Cy5.5-labeled dimeric NGR peptide by Guoquan Li; Yan Xing; Jing Wang; Peter S. Conti; Kai Chen (1547-1556).
In this study, we synthesized a novel Cy5.5-labeled dimeric NGR peptide (Cy5.5-NGR2) via bioorthogonal click chemistry, and evaluated the utility of Cy5.5-NGR2 for near-infrared fluorescence imaging of CD13 receptor expression in vivo. The dimeric NGR peptide (NGR2) was conjugated with an alkyne-containing PEG unit followed by mixing with an azide-terminated Cy5.5 fluorophore (Cy5.5-N3) to afford Cy5.5-NGR2. The probe was subject to in vitro and in vivo evaluations. The bioorthogonal click chemistry provided a rapid conjugation of the alkyne-containing NGR2 with Cy5.5-N3 in a quantitative yield within 15 min. The laser confocal microscopy revealed that binding of Cy5.5-NGR2 to CD13 receptor is target-specific as demonstrated in CD13-positive HT-1080 cells, CD13-negative MCF-7 cells, and a blocking study in HT-1080 cells. For in vivo optical imaging, Cy5.5-NGR2 exhibited rapid HT-1080 tumor targeting at 0.5 h postinjection (pi), and highest tumor-to-background contrast at 2 h pi. The CD13-specific tumor accumulation of Cy5.5-NGR2 was accomplished by a blocking study with unlabeled NGR peptide in HT-1080 tumor bearing mice. The tumor-to-muscle ratio of Cy5.5-NGR2 at 2 h pi reached 2.65 ± 0.13 in the non-blocking group vs. 1.05 ± 0.06 in the blocking group. The results from ex vivo imaging were consistent with the in vivo findings. We concluded that Cy5.5-NGR2 constructed by bioorthogonal click chemistry is a promising molecular probe, not only allowing the NIR optical imaging of CD13 overexpressed tumors, but also having the potential to facilitate noninvasive monitoring of CD13-targeted tumor therapy.
Keywords: Molecular imaging probe; NGR peptide; Fluorescence imaging; CD13 receptor; Tumor vasculature

Analysis of polyamines in biological samples by HPLC involving pre-column derivatization with o-phthalaldehyde and N-acetyl-l-cysteine by Zhaolai Dai; Zhenlong Wu; Junjun Wang; Xiaoqiu Wang; Sichao Jia; Fuller W. Bazer; Guoyao Wu (1557-1564).
Polyamines (putrescine, spermine and spermidine) play a crucial role in the regulation of cell growth, differentiation, death and function. Accurate measurement of these substances is essential for studying their metabolism in cells. This protocol describes detailed procedures for sample preparation and HPLC analysis of polyamines and related molecules (e.g., agmatine and cadaverine) in biological samples. The method is optimized for the deproteinization of samples, including biological fluids (e.g., 10 μl), plant and animal tissues (e.g., 50 mg), and isolated/cultured cells (e.g., 1 × 106 cells). The in-line reaction of polyamines with o-phthalaldehyde and N-acetyl-l-cysteine yields fluorescent derivatives which are separated on a reversed-phase C18 column and detected by a fluorometer at an excitation wavelength of 340 nm and an emission wavelength of 450 nm. The total running time for each sample (including column regeneration on the automated system) is 30 min. The detection limit is 0.5 nmol/ml or 0.1 nmol/mg tissue in biological samples. The assays are linear between 1 and 50 μM for each of the polyamines. The accuracy (the nearness of an experimental value to the true value) and precision (agreement between replicate measurement) of the HPLC method are 2.5–4.2 % and 0.5–1.4 %, respectively, for biological samples, depending on polyamine concentrations and sample type. Our HPLC method is highly sensitive, specific, accurate, easily automated, and capable for the analysis of samples with different characteristics and small volume/amount, and provides a useful research tool for studying the biochemistry, physiology, and pharmacology of polyamines and related substances.
Keywords: Polyamines; Derivatization; o-Phthalaldehyde; N-Acetyl-l-cysteine; HPLC

The Center for Optimized Structural Studies (COSS) platform for automation in cloning, expression, and purification of single proteins and protein–protein complexes by Georg Mlynek; Anita Lehner; Jana Neuhold; Sarah Leeb; Julius Kostan; Alexej Charnagalov; Peggy Stolt-Bergner; Kristina Djinović-Carugo; Nikos Pinotsis (1565-1582).
Expression in Escherichia coli represents the simplest and most cost effective means for the production of recombinant proteins. This is a routine task in structural biology and biochemistry where milligrams of the target protein are required in high purity and monodispersity. To achieve these criteria, the user often needs to screen several constructs in different expression and purification conditions in parallel. We describe a pipeline, implemented in the Center for Optimized Structural Studies, that enables the systematic screening of expression and purification conditions for recombinant proteins and relies on a series of logical decisions. We first use bioinformatics tools to design a series of protein fragments, which we clone in parallel, and subsequently screen in small scale for optimal expression and purification conditions. Based on a scoring system that assesses soluble expression, we then select the top ranking targets for large-scale purification. In the establishment of our pipeline, emphasis was put on streamlining the processes such that it can be easily but not necessarily automatized. In a typical run of about 2 weeks, we are able to prepare and perform small-scale expression screens for 20–100 different constructs followed by large-scale purification of at least 4–6 proteins. The major advantage of our approach is its flexibility, which allows for easy adoption, either partially or entirely, by any average hypothesis driven laboratory in a manual or robot-assisted manner.
Keywords: Construct optimization; Ligation-indepedent cloning; Expression screening; Optimized protein production; Structural biology

l-Theanine elicits umami taste via the T1R1 + T1R3 umami taste receptor by Masataka Narukawa; Yasuka Toda; Tomoya Nakagita; Yukako Hayashi; Takumi Misaka (1583-1587).
l-Theanine is a unique amino acid present in green tea. It elicits umami taste and has a considerable effect on tea taste and quality. We investigated l-theanine activity on the T1R1 + T1R3 umami taste receptor. l-Theanine activated T1R1 + T1R3-expressing cells and showed a synergistic response with inosine 5′-monophosphate. The site-directed mutagenesis analysis revealed that l-theanine binds to l-amino acid binding site in the Venus flytrap domain of T1R1. This study shows that l-theanine elicits an umami taste via T1R1 + T1R3.
Keywords: l-Theanine; Umami; Synergy; T1R1 + T1R3