scholarly journals Cloning, Expression, Characterization, and Antioxidant Protection of Glutaredoxin3 From Psychrophilic Bacterium Psychrobacter sp. ANT206

2021 ◽  
Vol 12 ◽  
Author(s):  
Yatong Wang ◽  
Yanhua Hou ◽  
Quanfu Wang
Keyword(s):  
Catalytic Activity ◽  
Point Mutations ◽  
Cd Spectroscopy ◽  
Biochemical Properties ◽  
Site Directed Mutagenesis ◽  
Psychrophilic Bacterium ◽  
Amino Acid Residues ◽  
Salt Bridges ◽  
Active Site Motif ◽  
Expression Characterization

Glutaredoxins (Grxs) are proteins that catalyze the glutathione (GSH)-dependent reduction of protein disulfides. In this study, a Grx-related gene (264 bp), encoding a Ps-Grx3, was cloned from Psychrobacter sp. ANT206. Sequence analysis indicated the presence of the active site motif CPYC in this protein. Homology modeling showed that Ps-Grx3 had fewer hydrogen bonds and salt bridges, as well as a lower Arg/(Arg + Lys) ratio than its mesophilic homologs, indicative of an improved catalytic ability at low temperatures. Site-directed mutagenesis demonstrated that the Cys13, Pro14, and Cys16 sites were essential for the catalytic activity of Ps-Grx3, while circular dichroism (CD) spectroscopy confirmed that point mutations in these amino acid residues led to the loss or reduction of enzyme activity. Furthermore, analysis of the biochemical properties of Ps-Grx3 showed that the optimum temperature of this enzyme was 25 °C. Importantly, Ps-Grx3 was more sensitive to tBHP and CHP than to H2O2, and retained approximately 40% activity even when the H2O2 concentration was increased to 1 mm Regarding substrate specificity, Ps-Grx3 had a higher affinity for HED, L-cystine, and DHA than for S-sulfocysteine and BSA. We also investigated the DNA-protective ability of Ps-Grx3 using the pUC19 plasmid, and found that Ps-Grx3 could protect supercoiled DNA from oxidation-induced damage at 15°C for 1.5 h. This study provides new insights into the structure and catalytic activity of a cold-adapted Grx3.

Block of Human Heart hH1 Sodium Channels by the Enantiomers of Bupivacaine

2000 ◽  
Vol 93 (4) ◽  
pp. 1022-1033 ◽  
Author(s):  
Carla Nau ◽  
Sho-Ya Wang ◽  
Gary R. Strichartz ◽  
Ging Kuo Wang
Keyword(s):  
Human Heart ◽  
Point Mutations ◽  
Cell Voltage ◽  
Site Directed Mutagenesis ◽  
Na Channel ◽  
Amino Acid Residues ◽  
Na Channels ◽  
State Dependent ◽  
Positively Charged

Background S(-)-bupivacaine reportedly exhibits lower cardiotoxicity but similar local anesthetic potency compared with R(+)-bupivacaine. The bupivacaine binding site in human heart (hH1) Na+ channels has not been studied to date. The authors investigated the interaction of bupivacaine enantiomers with hH1 Na+ channels, assessed the contribution of putatively relevant residues to binding, and compared the intrinsic affinities to another isoform, the rat skeletal muscle (mu1) Na+ channel. Methods Human heart and mu1 Na+ channel alpha subunits were transiently expressed in HEK293t cells and investigated during whole cell voltage-clamp conditions. Using site-directed mutagenesis, the authors created point mutations at positions hH1-F1760, hH1-N1765, hH1-Y1767, and hH1-N406 by introducing the positively charged lysine (K) or the negatively charged aspartic acid (D) and studied their influence on state-dependent block by bupivacaine enantiomers. Results Inactivated hH1 Na+ channels displayed a weak stereoselectivity with a stereopotency ratio (+/-) of 1.5. In mutations hH1-F1760K and hH1-N1765K, bupivacaine affinity of inactivated channels was reduced by approximately 20- to 40-fold, in mutation hH1-N406K by approximately sevenfold, and in mutations hH1-Y1767K and hH1-Y1767D by approximately twofold to threefold. Changes in recovery of inactivated mutant channels from block paralleled those of inactivated channel affinity. Inactivated hH1 Na+ channels exhibited a slightly higher intrinsic affinity than mu1 Na+ channels. Conclusions Differences in bupivacaine stereoselectivity and intrinsic affinity between hH1 and mu1 Na+ channels are small and most likely of minor clinical relevance. Amino acid residues in positions hH1-F1760, hH1-N1765, and hH1-N406 may contribute to binding of bupivacaine enantiomers in hH1 Na+ channels, whereas the role of hH1-Y1767 remains unclear.

scholarly journals Activation of Ha-ras p21 by substitution, deletion, and insertion mutations.

1985 ◽  
Vol 5 (8) ◽  
pp. 1809-1813 ◽  
Author(s):  
R G Chipperfield ◽  
S S Jones ◽  
K M Lo ◽  
R A Weinberg
Keyword(s):  
Amino Acid ◽  
Point Mutations ◽  
Normal Function ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Amino Acid Residues ◽  
Transforming Activity ◽  
Ras P21 ◽  
Ras Oncogenes ◽  
Insertion Mutations

The transforming activity of naturally arising ras oncogenes results from point mutations that affect residue 12 or 61 of the encoded 21-kilodalton protein (p21). By use of site-directed mutagenesis, we showed that deletions and insertions of amino acid residues in the region of residue 12 are also effective in conferring oncogenic activity on p21. Common to these various alterations is the disruption that they create in this domain of the protein, which we propose results in the inactivation of a normal function of the protein.

Implications of Stisa2 catalytic residue restoration through site directed mutagenesis

2016 ◽  
Vol 42 (2) ◽  
Author(s):  
Hasnain Hussain ◽  
Nikson Fatt Ming Chong
Keyword(s):  
Catalytic Activity ◽  
Catalytic Triad ◽  
Site Directed Mutagenesis ◽  
Amino Acid Residues ◽  
Qualitative And Quantitative Analysis ◽  
Conserved Residues ◽  
Overlap Extension Pcr ◽  
Overlap Extension ◽  
Catalytic Network ◽  
And Function

AbstractObjective:Restoration of catalytic activity of Isa2 fromMethods:The six conserved amino acid residues absent in the Stisa2 gene were restored by mutation using the overlap extension PCR and the asymmetrical overlap extension PCR methods. Next, mutant Stisa2 with restored catalytic residues was expressed inResults:Both qualitative and quantitative analysis showed that the restoration of the conserved residues in the catalytic site did not restore starch debranching activity. Molecular modeling showed greater than expected distances between the catalytic triad in mutant Stisa2. These additional distances are likely to prevent hydrogen bonding which stabilizes the reaction intermediate, and are critical for catalytic activity.Conclusions:These results suggest that during evolution, mutations in other highly conserved regions have caused significant changes to the structure and function of the catalytic network. Catalytically inactive Isa2, which is conserved in starch-producing plants, has evolved important non-catalytic roles such as in substrate binding and in regulating isoamylase activity.

scholarly journals Processing of Pro–Brain Natriuretic Peptide Is Suppressed by O-Glycosylation in the Region Close to the Cleavage Site

2009 ◽  
Vol 55 (3) ◽  
pp. 489-498 ◽  
Author(s):  
Alexander G Semenov ◽  
Alexander B Postnikov ◽  
Natalia N Tamm ◽  
Karina R Seferian ◽  
Natalia S Karpova ◽  
...  
Keyword(s):  
Brain Natriuretic Peptide ◽  
Natriuretic Peptide ◽  
Cleavage Site ◽  
Gel Filtration ◽  
Biochemical Properties ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Amino Acid Residues ◽  
Hek 293 ◽  
Processing Mechanisms

Abstract Background: Processing of the brain natriuretic peptide (BNP) precursor, proBNP, is a convertase-dependent reaction that produces 2 molecules—the active BNP hormone and the N-terminal part of proBNP (NT-proBNP). Although proBNP was first described more than 15 years ago, very little is known about the cellular mechanism of its processing. The study of proBNP processing mechanisms is important, because processing impairments could be associated with the development of heart failure (HF). Methods: The biochemical properties of recombinant proBNP and NT-proBNP and the same molecules derived from the blood of HF patients were analyzed by gel-filtration chromatography, site-directed mutagenesis, and different immunochemical methods with a panel of monoclonal antibodies (MAbs). Results: Part of the proBNP molecule (amino acid residues 61–76) located near the cleavage site was inaccessible to specific MAbs because of the presence of O-glycans, whereas the same region in NT-proBNP was completely accessible. We demonstrated that a convertase (furin) could effectively cleave deglycosylated (but not intact) proBNP. Of several mutant proBNP forms produced in a HEK 293 cell line, only the T71A variant was effectively processed in the cell. Conclusions: Only proBNP that was not glycosylated in the region of the cleavage site could effectively be processed into BNP and NT-proBNP. Site-directed mutagenesis enabled us to ascertain the unique suppressing role of T71-bound O-glycan in proBNP processing.

scholarly journals Effect of Point Mutations on Structural and Allergenic Properties of the Lentil Allergen Len c 3

Membranes ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 939
Author(s):  
Daria N. Melnikova ◽  
Ekaterina I. Finkina ◽  
Ivan V. Bogdanov ◽  
Anastasia A. Ignatova ◽  
Natalia S. Matveevskaya ◽  
...  
Keyword(s):  
Amino Acid ◽  
Binding Capacity ◽  
Point Mutations ◽  
Site Directed Mutagenesis ◽  
Amino Acid Residues ◽  
Lipid Transfer ◽  
Ige Binding ◽  
Allergenic Potential ◽  
Binding Epitope ◽  
Clinically Significant

Plant lipid transfer proteins (LTPs) are known to be clinically significant allergens capable of binding various lipid ligands. Recent data showed that lipid ligands affected the allergenic properties of plant LTPs. In this work, we checked the assumption that specific amino acid residues in the Len c 3 structure can play a key role both in the interaction with lipid ligands and IgE-binding capacity of the allergen. The recombinant analogues of Len c 3 with the single or double substitutions of Thr41, Arg45 and/or Tyr80 were obtained by site-directed mutagenesis. All these amino acid residues are located near the “bottom” entrance to the hydrophobic cavity of Len c 3 and are likely included in the IgE-binding epitope of the allergen. Using a bioinformatic approach, circular dichroism and fluorescence spectroscopies, ELISA, and experiments mimicking the allergen Len c 3 gastroduodenal digestion we showed that the substitution of all the three amino acid residues significantly affected structural organization of this region and led both to a change of the ligand-binding capacity and the allergenic potential of Len c 3.

Analysis of essential carboxylic amino acid residues for catalytic activity of fungal chitosanases by site-directed mutagenesis

2005 ◽  
Vol 100 (5) ◽  
pp. 545-550 ◽  
Author(s):  
Makoto Shimosaka ◽  
Kazuaki Sato ◽  
Naohide Nishiwaki ◽  
Takashi Miyazawa ◽  
Mitsuo Okazaki
Keyword(s):  
Catalytic Activity ◽  
Amino Acid ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Amino Acid Residues

scholarly journals Characterization of the Critical Amino Acids of anAspergillus parasiticus Cytochrome P-450 Monooxygenase Encoded by ordA That Is Involved in the Biosynthesis of Aflatoxins B1, G1, B2, and G2

1998 ◽  
Vol 64 (12) ◽  
pp. 4834-4841 ◽  
Author(s):  
Jiujiang Yu ◽  
Perng-Kuang Chang ◽  
Kenneth C. Ehrlich ◽  
Jeffrey W. Cary ◽  
Beverly Montalbano ◽  
...  
Keyword(s):  
Amino Acid ◽  
Point Mutations ◽  
Site Directed Mutagenesis ◽  
Amino Acid Residues ◽  
Oxidoreductase Activity ◽  
Monooxygenase Activity ◽  
Pathway Gene ◽  
Chromosomal Walking ◽  
Aflatoxin B ◽  
Cytochrome P 450

The conversion of O-methylsterigmatocystin (OMST) and dihydro-O-methylsterigmatocystin to aflatoxins B1, G1, B2, and G2requires a cytochrome P-450 type of oxidoreductase activity.ordA, a gene adjacent to the omtA gene, was identified in the aflatoxin-biosynthetic pathway gene cluster by chromosomal walking in Aspergillus parasiticus. The ordA gene was a homolog of the Aspergillus flavus ord1 gene, which is involved in the conversion of OMST to aflatoxin B1. Complementation of A. parasiticus SRRC 2043, an OMST-accumulating strain, with theordA gene restored the ability to produce aflatoxins B1, G1, B2, and G2. TheordA gene placed under the control of the GAL1promoter converted exogenously supplied OMST to aflatoxin B1 in Saccharomyces cerevisiae. In contrast, the ordA gene homolog in A. parasiticus SRRC 2043, ordA1, was not able to carry out the same conversion in the yeast system. Sequence analysis revealed that theordA1 gene had three point mutations which resulted in three amino acid changes (His-400→Leu-400, Ala-143→Ser-143, and Ile-528→Tyr-528). Site-directed mutagenesis studies showed that the change of His-400 to Leu-400 resulted in a loss of the monooxygenase activity and that Ala-143 played a significant role in the catalytic conversion. In contrast, Ile-528 was not associated with the enzymatic activity. The involvement of the ordA gene in the synthesis of aflatoxins G1, and G2 inA. parasiticus suggests that enzymes required for the formation of aflatoxins G1 and G2 are not present in A. flavus. The results showed that in addition to the conserved heme-binding and redox reaction domains encoded by ordA, other seemingly domain-unrelated amino acid residues are critical for cytochrome P-450 catalytic activity. TheordA gene has been assigned to a new cytochrome P-450 gene family named CYP64 by The Cytochrome P450 Nomenclature Committee.

scholarly journals Riboflavin Synthase ofEscherichia coli

2001 ◽  
Vol 276 (15) ◽  
pp. 11524-11530 ◽  
Author(s):  
Boris Illarionov ◽  
Kristina Kemter ◽  
Sabine Eberhardt ◽  
Gerald Richter ◽  
Mark Cushman ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Catalytic Activity ◽  
Amino Acid ◽  
Binding Sites ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Sequence Motif ◽  
Amino Acid Residues ◽  
Terminal Sequence ◽  
Substrate Binding Sites

Conserved amino acid residues of riboflavin synthase fromEscherichia coliwere modified by site-directed mutagenesis. Replacement or deletion of phenylalanine 2 afforded catalytically inactive proteins. S41A and H102Q mutants had substantially reduced reaction velocities. Replacements of various other conserved polar residues had little impact on catalytic activity.19F NMR protein perturbation experiments using a fluorinated intermediate analog suggest that the N-terminal sequence motif MFTG is part of one of the substrate-binding sites of the protein.

scholarly journals The C-Terminal Region of Bacteroides fragilis Toxin Is Essential to Its Biological Activity

2006 ◽  
Vol 74 (10) ◽  
pp. 5595-5601 ◽  
Author(s):  
Cynthia L. Sears ◽  
Simy L. Buckwold ◽  
Jai W. Shin ◽  
Augusto A. Franco
Keyword(s):  
Biological Activity ◽  
Amino Acid ◽  
Point Mutations ◽  
Bacteroides Fragilis ◽  
Terminal Region ◽  
Site Directed Mutagenesis ◽  
Amino Acid Residues ◽  
Wild Type ◽  
Reverse Transcription Pcr ◽  
C Terminus

ABSTRACT To evaluate the role of the C-terminal region in Bacteroides fragilis toxin (BFT) activity, processing, and secretion, sequential C-terminal truncation and point mutations were created by site-directed mutagenesis. Determination of BFT activity on HT29/C1 cells, cleavage of E-cadherin, and the capacity to induce interleukin-8 secretion by wild-type BFT and C-terminal deletion mutants showed that deletion of only 2 amino acid residues at the C terminus significantly reduced BFT biological activity and deletion of eight or more amino acid residues obliterated BFT biologic activity. Western blot and reverse transcription-PCR analyses indicated that BFT mutants lacking seven or fewer amino acid residues in the C-terminal region are processed and expressed similar to wild-type BFT. However, BFT mutants lacking eight or more amino acids at the C terminus are expressed similar to wild-type BFT but are unstable. We concluded that the C terminus of BFT is not tolerant of modest amino acid deletions, suggesting that it is biologically important for BFT activity.

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