Protein expression and purification最新文献

{"title":"The heterogeneous expression, extraction, and purification of recombinant Caldanaerobacter subterraneus subsp. tengcongensis apurine/apyrimidine endonuclease in Escherichia coli","authors":"Wanli Guo ,&nbsp;Dajin Wang ,&nbsp;Wei Chen ,&nbsp;Chuyang Rao ,&nbsp;Yunxuan Tang ,&nbsp;Wangfeng Li","doi":"10.1016/j.pep.2024.106621","DOIUrl":"10.1016/j.pep.2024.106621","url":null,"abstract":"<div><div>Thermostable apurinic/apyrimidinic (AP) endonuclease (TtAP), cloned from <em>Caldanaerobacter subterraneus</em> subsp. tengcongensis, is an exonuclease III (Exo III) family protein with high-heat resistance, has activities of AP site endonuclease, 3′–5′ exonuclease, and 3′-nuclease, and facilitates efficient amplification of lengthy DNA fragments in PCR. However, the research of the combinant <em>TtAP</em> in <em>Escherichia coli</em> with its expression, large-scale extraction and purification of its protein was limited. In this study, we optimized the codons of TtAP gene for expression in <em>E. coli</em> and constructed a fusion gene encoding TtAP with a 6His tag (<em>TtAP-6His</em>). <em>TtAP-6His</em> was put into vector <em>pET-30a</em>⁽⁺⁾ to form the expression vector <em>pET-30a</em>⁽⁺⁾<em>-TtAP-6His</em>, and was then introduced into <em>E. coli</em> strain Rosetta (DE3). We established a systematic process for the extraction of TtAP protein using 5 liters of bacterial suspension, including the optimization of IPTG induction time (6 h), followed by protein extraction using enzymolysis buffers, the heat treatment of temperature (70 °C) with 60 min to remove impurity, precipitation with ammonium sulfate (55 %), protein purification with Ni-affinity chromatography, and the enzyme activities finally were determined. The purification yield of TtAP-6His ranged from 73.67 to 115.25 mg/L (47 KU/mg).</div></div>","PeriodicalId":20757,"journal":{"name":"Protein expression and purification","volume":"226 ","pages":"Article 106621"},"PeriodicalIF":1.4,"publicationDate":"2024-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142626847","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Nature of recombinant human serum amyloid A1 in Escherichia coli and its preferable approach for purification","authors":"Saira Ahmad ,&nbsp;Qurratulann Afza Gardner ,&nbsp;Nisar Ahmad Shakir ,&nbsp;Sabahat Gulzar ,&nbsp;Naseema Azim ,&nbsp;Muhammad Akhtar","doi":"10.1016/j.pep.2024.106620","DOIUrl":"10.1016/j.pep.2024.106620","url":null,"abstract":"<div><div>Serum amyloid A1 (SAA1) is an apolipoprotein which is involved in amyloid A amyloidosis (AA) by forming fibrils. The process of fibrillation is still being explored and holds challenges in recombinant expression and purification of SAA1. This study deals with the preferable approach for the expression and purification of SAA1 which is normally toxic and unstable to express without using any fusion-tag. Complete soluble expression of SAA1 was obtained without the use of additional tag, in terrific broth, supplemented with 3 % ethanol at 30 °C. Soluble fraction of SAA1 was initially treated with salting-out using ammonium sulphate giving 1.5 M salt concentration to avoid SAA1 protein precipitation along with unwanted proteins. The soluble fraction of SAA1 after salting-out was purified by two individual chromatographic approaches: One anion exchange and second reverse phase chromatography. The yield of purified SAA1 was 3 times greater by anion exchange than reverse phase chromatography. MALDI-TOF analysis of purified SAA1 showed 11813 Da for intact protein and proteome analysis revealed greater than 90 % sequence coverage by MASCOT. The subunit interaction showed hexamer form at basic pH which was analyzed by size exclusion chromatography. The fibrillation activity of SAA1 was found to be 10–15 times higher in basic media at 43 °C than 37 °C. Our research demonstrates successful expression and purification of wild-type human recombinant SAA1. The cost-effective radical approach employed for purification of SAA1 is crucial for thorough protein characterization particularly, mechanisms of protein aggregation involved in amyloidosis.</div></div>","PeriodicalId":20757,"journal":{"name":"Protein expression and purification","volume":"227 ","pages":"Article 106620"},"PeriodicalIF":1.4,"publicationDate":"2024-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142591340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Trehalose-6-phosphate phosphatase expression and enzymatic properties of Fusarium graminearum","authors":"Xuebiao Zhang ,&nbsp;Le Chen ,&nbsp;Zhong Ni ,&nbsp;Chao Xu ,&nbsp;Qinyan Wu ,&nbsp;Yiqing Zhuang","doi":"10.1016/j.pep.2024.106619","DOIUrl":"10.1016/j.pep.2024.106619","url":null,"abstract":"<div><div>This study presents an exhaustive characterization of the enzymatic attributes and structural properties of trehalose-6-phosphate phosphatase (TPP) derived from <em>Fusarium graminearum</em>. Enzyme activity was evaluated through a meticulously designed enzymatic assay. The findings indicate that the molecular weight of the enzyme is approximately 99.8 kDa, with an optimal reaction temperature and pH of 40 °C and 6.5, respectively. Magnesium ions (Mg²⁺) markedly enhance the enzymatic activity, resulting in a specific activity of 1.795 U/μg. Kinetic analysis revealed a <em>K</em>_m value of 0.96 μmol/L and a <em>V</em>_max of 15.79 μmol/L/min. Subsequent computational analysis elucidated the three-dimensional architecture of the enzyme and identified the binding site for the substrate trehalose-6-phosphate (T6P). T6P was found to form hydrogen bonds with TPP at residues Lys754, Arg720, His665, Glu758, and Asn756. Additionally, hydrophobic interactions were observed between T6P and residues Phe802, Ile610, Asp801, Pro752, and Gly753. The binding energy calculated for the T6P-TPP complex stood at −5.7 kcal/mol.</div></div>","PeriodicalId":20757,"journal":{"name":"Protein expression and purification","volume":"226 ","pages":"Article 106619"},"PeriodicalIF":1.4,"publicationDate":"2024-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142606002","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Efficient periplasmic expression of active lysyl endopeptidase and optimizing the purification methods","authors":"Zahra Pourani ,&nbsp;Malihe Keramati ,&nbsp;Samira Komijani ,&nbsp;Majid Golkar ,&nbsp;Reza Ahangari Cohan ,&nbsp;Nastaran Mohseni ,&nbsp;Vahideh Valizadeh","doi":"10.1016/j.pep.2024.106618","DOIUrl":"10.1016/j.pep.2024.106618","url":null,"abstract":"<div><div>Recombinant production of lysyl endopeptidase (Lys-C) which is frequently used in proteomics is still challenging due to its complex structure. Herein, periplasmic expression and determining effective factors for recovery of the active enzyme were investigated. The codon-optimized Lys-C gene was cloned into pET26b (+) for periplasmic expression in <em>E. coli</em> Rosetta (DE3). The following parameters affecting expression level and activity of Lys-C were investigated including IPTG concentration (0.05–1 mM), cell density (OD₆₀₀: 0.45–0.8) at induction time, presence of reducing agents (glutathione or cysteine, 0–10 mM) in culture medium or periplasmic extraction buffers, and harvesting time (6 or 20 h). Lys-C was then purified by DEAE and Ni-NTA chromatography methods. The highest expression level was obtained at 0.05 mM IPTG (5.49 %), also 8 mM cysteine, induction at OD_600: 0.45 and 6 h incubation increased enzyme activity to 23.5 %, 13.3 %, and 76.4 %, respectively. The enzyme activity of Lys-C in the presence of 4 mM glutathione and extraction buffers containing 2 mM 2-mercaptoethanol (2 ME) was 81.6 % higher than the condition without reducing agents. Also, 8 mM cysteine in the culture medium and 2 mM 2 ME in extraction increased the activity up to 29.7 %. Moreover, optimization of purification process enhanced the enzyme activity from 0.217 mU to 1.76 mU. Statistical analysis showed the examined parameters significantly affected enzyme activity (p &lt; 0.05). The presence of the reducing agents in the culture medium and extraction buffers presumably improves the Lys-C folding and increases the enzyme activity.</div></div>","PeriodicalId":20757,"journal":{"name":"Protein expression and purification","volume":"226 ","pages":"Article 106618"},"PeriodicalIF":1.4,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142591338","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Human parvovirus B19 virus-like particle formation in Nicotiana benthamiana","authors":"Sakika Kimura ,&nbsp;Jiahui Ong ,&nbsp;Atsushi Kasai ,&nbsp;Shinji Akada ,&nbsp;Hirotaka Ebina ,&nbsp;Michiko Sasabe ,&nbsp;Eiji Morita","doi":"10.1016/j.pep.2024.106616","DOIUrl":"10.1016/j.pep.2024.106616","url":null,"abstract":"<div><div>There has been a surge in the interest to utilize plants as hosts for producing vaccine antigens. In this study, we demonstrated the successful expression of the human parvovirus B19 (B19V) capsid protein (VP2) in <em>Nicotiana benthamiana</em> cells. The B19V VP1 and VP2 genes were cloned under the control of estrogen-inducible promoters and transiently expressed in <em>N. benthamiana</em> leaves using the agroinfiltration method. The addition of estrogen significantly boosted the expression of VP2. Furthermore, codon optimization of the VP2 sequence resulted in over a 30-fold increase in its expression compared with that of the wild-type. Analysis of negatively stained samples by sucrose density gradient ultracentrifugation and electron microscopy revealed that the expressed VP2 proteins formed spherical particles with diameters of approximately 20 nm. Immunostaining analysis of protoplasts derived from VP2-expressing <em>N. benthamiana</em> leaves indicated that VP2 signals were predominantly localized in the cytoplasm. These findings strongly suggested that B19V VP2 assembles and formed virus-like particles (VLPs) within the cytoplasm of <em>N. benthamiana</em> cells, presenting a promising method for producing B19V VLPs in plant systems.</div></div>","PeriodicalId":20757,"journal":{"name":"Protein expression and purification","volume":"226 ","pages":"Article 106616"},"PeriodicalIF":1.4,"publicationDate":"2024-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142564768","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Detection and optimization of microbial expression systems for extracellular production and purification of Ca2+-responsive phase-changing annexin fusions","authors":"Jinjing Li,&nbsp;Baokang Wu,&nbsp;Yiting Ji,&nbsp;Shuncheng Zhang,&nbsp;Yuanyuan Ge,&nbsp;Jun Fan","doi":"10.1016/j.pep.2024.106617","DOIUrl":"10.1016/j.pep.2024.106617","url":null,"abstract":"<div><div>Previously, we identified the human annexin A1 as a purification tag for column-free purification with gentler calcium-responsive precipitation. In this work, we used the annexin A1 tagged green fluorescent protein constructs for detecting extracellular production in <em>Escherichia coli</em>, <em>Bacillus subtilis</em>, and <em>Pichia pastoris</em>, and identified that the leaderless fusion protein was transported extracellularly in <em>E. coli</em> with supply of additives including Triton X-100. The coexpressed enzymes, culture compositions, and induction conditions in <em>E. coli</em> extracellular expression systems were optimized. With coexpression of phospholipase C from <em>Bacillus cereus</em> and addition of 0.2 % Triton X-100 after induction for 60 h at 28 °C, the annexin A1 tagged green fluorescent protein and 5-aminolevulinate dehydratase from <em>E. coli</em> were overexpressed and purified from lysogeny broth by precipitation with 20 mM Ca²⁺ and redissolution with 25 mM EDTA with the acceptable protein purities and recoveries. The silica binding peptide was fused to the annexin A1 tagged fluorescent protein fusion for successive affinity precipitation and purification. With incubation of the specific protease, the released tag-free protein displayed higher purity via on-resin cleavage than that through cleavage of the free fusion protein. The tandem tag is applicable for two-step purification of small or large amounts of other fusion proteins in the culture and recovery of tag-free proteins at low cost.</div></div>","PeriodicalId":20757,"journal":{"name":"Protein expression and purification","volume":"226 ","pages":"Article 106617"},"PeriodicalIF":1.4,"publicationDate":"2024-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142564752","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Functional expression of the chimera proteins of Nav1.7 and NavAb in Escherichia coli","authors":"Tomohiro Yamaguchi,&nbsp;Toshiaki Okada,&nbsp;Tadashi Kimura","doi":"10.1016/j.pep.2024.106615","DOIUrl":"10.1016/j.pep.2024.106615","url":null,"abstract":"<div><div>Na_v1.7 is a eukaryotic voltage-dependent Na channel (Na_v) family membrane protein and has four channel domains and four voltage sensor domains (VSD-I–IV). It is involved in pain perception, and VSDs that differ significantly by Na_v subtype are targeted in the development of Na_v1.7-specific inhibitors. This is expected to result in neuropathic pain treatments with fewer side effects. We previously reported on intra-periplasm secretion and selection (PERISS), a peptide drug discovery system that targets membrane proteins by co-expressing a peptide library and a target membrane protein. For PERISS screening of VSD-specific new Na_v1.7 inhibitors, the chimera protein (Na_vAb/1.7VSD) of Na_v from prokaryotic <em>Arcobacter butzleri</em> (Na_vAb), in which extracellular loops of VSD were replaced with homologous loops from Na_v1.7, serves as an effective model. This is because Na_vAb harbors only one VSD and the biological activity of Na_vAb/1.7VSD was previously confirmed. To date, Na_vAb/1.7VSD has only been found to be expressed in insect cells. In this study, we report on the expression and channel activity of Na_vAb/1.7VSD-II in <em>Escherichia coli</em> (<em>E. coli</em>). The expression of this protein in the inner membrane of <em>E. coli</em> was confirmed by western blotting. Channel activity was assessed by measuring the channel currents of the purified recombinant proteins and inhibition using a Na_v1.7-specific peptide inhibitor. The results indicate that Na_vAb/1.7VSD-II was functionally expressed in <em>E. coli</em>, providing empirical support for the discovery of new VSD-specific Na_v1.7 inhibitors using the PERISS screening method.</div></div>","PeriodicalId":20757,"journal":{"name":"Protein expression and purification","volume":"226 ","pages":"Article 106615"},"PeriodicalIF":1.4,"publicationDate":"2024-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142564756","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Expression, purification and characterization of a novel triple fusion protein developed for the immunotherapy of survivin positive cancers","authors":"Ambreen Rashid ,&nbsp;Mohammad Azad ,&nbsp;Anuja Krishnan ,&nbsp;Jagdish C. Gupta ,&nbsp;G.P. Talwar","doi":"10.1016/j.pep.2024.106614","DOIUrl":"10.1016/j.pep.2024.106614","url":null,"abstract":"<div><div>Survivin is an inhibitor of apoptosis, and expressed in a large number of cancers. As Survivin expression is very low in normal tissues, it assumes significance as a prominent target for tumor diagnosis, prognosis and developing anti-cancer therapies. We report development of a novel triple fusion protein for a prospective vaccine against Survivin in targeted cancer immunotherapy. A gene was synthesized by combining the nucleotides encoding human origin Survivin and heat-labile enterotoxin of <em>Escherichia coli</em> (LTB). Further, nucleotides corresponding to single chain variable fragment (scFv) of a monoclonal having affinity for DEC205 receptor present on dendritic cells, were also incorporated into the gene sequence. This complete gene was expressed to a triple fusion recombinant protein using a bacterial expression vector under the control of robust bacteriophage T7 promoter. The recombinant _DCSurvivin-LTB protein, with a size of approximately 60 kDa, was purified from the inclusion bodies using affinity based Ni-NTA columns. The purified protein was confirmed by the Western blot, and further characterized with circular dichroism, fluorescence spectroscopy and mass spectroscopy. This molecularly adjuvanted Survivin fusion protein designed to deliver to the dendritic cells for better antigen processing, elicited a stronger anti-Survivin immune response compared to Survivin protein alone. It can be an effective vaccine in active and passive immunotherapies for Survivin expressing cancer cells.</div></div>","PeriodicalId":20757,"journal":{"name":"Protein expression and purification","volume":"226 ","pages":"Article 106614"},"PeriodicalIF":1.4,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142473255","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"N-linked glycosylation affects catalytic parameters and fluctuation of the active center of Aspergillus awamori exo-inulinase","authors":"Anna Dotsenko ,&nbsp;Yury Denisenko ,&nbsp;Ivan Zorov ,&nbsp;Aleksandra Rozhkova ,&nbsp;Igor Shashkov","doi":"10.1016/j.pep.2024.106613","DOIUrl":"10.1016/j.pep.2024.106613","url":null,"abstract":"<div><div>Heterogeneous expression of enzymes allows large-scale production with reduced costs. Changes in glycosylation often occur due to changes in the expression host. In the study, the catalytic and biochemical properties of <em>Aspergillus awamori</em> exo-inulinase 1 are compared for <em>A. awamori</em> and <em>Penicillium verruculosum</em> expression hosts. The tertiary structure contains seven sites of <em>N</em>-glycosylation, with two of them located near the active center. If expressed in <em>P. verruculosum</em>, the enzyme was four times less glycosylated and two times more active toward sucrose, raffinose, and stachyose due to an increase in <em>k</em>_<em>cat</em>. These substrates with a short chain of 2–4 monosaccharide units were used to characterize the interaction of the substrate with the amino acid residues in the active center while preventing the interaction of the substrate with <em>N</em>-linked glycans. Molecular dynamics simulations showed an increase in the fluctuation of the active center with an increase in the length of <em>N</em>-linked glycans. The fluctuation of the residues N40 and Q57, which interact with the hydroxyl group O5 of the fructose unit in the −1 subsite of the active center, was increased by 1.6 times. The fluctuation of the residue W335, which interacts with the hydroxyl group O1 of the fructose unit together with the catalytic residue D41 and affects the torsion angle geometry of the substrate molecules, was increased by 1.5 times. The residue R188, which analogously to W335 affects the torsion angle geometry of the substrate molecules, was also among the affected residues with a 1.2-fold increase in the fluctuation.</div></div>","PeriodicalId":20757,"journal":{"name":"Protein expression and purification","volume":"226 ","pages":"Article 106613"},"PeriodicalIF":1.4,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142366345","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Heterologous expression and purification of glutamate decarboxylase-1 from the model plant Arabidopsis thaliana: Characterization of the enzyme's in vitro truncation by thiol endopeptidase activity","authors":"Brittany S. Menard ,&nbsp;Kirsten H. Benidickson ,&nbsp;Lee Marie Raytek ,&nbsp;Wayne A. Snedden ,&nbsp;William C. Plaxton","doi":"10.1016/j.pep.2024.106612","DOIUrl":"10.1016/j.pep.2024.106612","url":null,"abstract":"<div><div>Plant glutamate decarboxylase (GAD) is a Ca²⁺-calmodulin (CaM) activated enzyme that produces γ-aminobutyrate (GABA) as the first committed step of the GABA shunt. Our prior research established that <em>in vivo</em> phosphorylation of AtGAD1 (AT5G17330) occurs at multiple N-terminal serine residues following Pi resupply to Pi-starved cell cultures of the model plant <em>Arabidopsis thaliana</em>. The aim of the current investigation was to purify recombinant AtGAD1 (rAtGAD1) following its expression in <em>Escherichia coli</em> to facilitate studies of the impact of phosphorylation on its kinetic properties. However, <em>in vitro</em> proteolytic truncation of an approximate 5 kDa polypeptide from the C-terminus of 59 kDa rAtGAD1 subunits occurred during purification. Immunoblotting demonstrated that most protease inhibitors or cocktails that we tested were ineffective in suppressing this partial rAtGAD1 proteolysis. Although the thiol modifiers N-ethylmaleimide or 2,2-dipyridyl disulfide negated rAtGAD1 proteolysis, they also abolished its GAD activity. This indicates that an essential -SH group is needed for catalysis, and that rAtGAD1 is susceptible to partial degradation either by an <em>E. coli</em> cysteine endopeptidase, or possibly via autoproteolytic activity. The inclusion of exogenous Ca²⁺/CaM facilitated the purification of non-proteolyzed rAtGAD1 to a specific activity of 27 (μmol GABA produced/mg) at optimal pH 5.8, while exhibiting an approximate 3-fold activation by Ca²⁺/CaM at pH 7.3. By contrast, the purified partially proteolyzed rAtGAD1 was &gt;40 % less active at both pH values, and only activated 2-fold by Ca²⁺/CaM at pH 7.3. These results emphasize the need to diagnose and prevent partial proteolysis before conducting kinetic studies of purified regulatory enzymes.</div></div>","PeriodicalId":20757,"journal":{"name":"Protein expression and purification","volume":"226 ","pages":"Article 106612"},"PeriodicalIF":1.4,"publicationDate":"2024-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142352672","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}