The hydrophobic core of Escherichia coli thioredoxin shows a high tolerance to nonconservative single amino acid substitutions

Biochemistry ◽  
1992 ◽  
Vol 31 (45) ◽  
pp. 11203-11209 ◽  
Author(s):  
H. W. Hellinga ◽  
R. Wynn ◽  
F. M. Richards
Keyword(s):  
Escherichia Coli ◽  
Amino Acid ◽  
Single Amino Acid ◽  
Amino Acid Substitutions ◽  
Hydrophobic Core ◽  
High Tolerance

Structural and functional consequences of single amino acid substitutions in the pyrimidine base binding pocket of Escherichia coli CMP kinase

FEBS Journal ◽  
2007 ◽  
Vol 274 (13) ◽  
pp. 3363-3373 ◽  
Author(s):  
Augustin Ofiteru ◽  
Nadia Bucurenci ◽  
Emil Alexov ◽  
Thomas Bertrand ◽  
Pierre Briozzo ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Amino Acid ◽  
Binding Pocket ◽  
Single Amino Acid ◽  
Amino Acid Substitutions ◽  
Pyrimidine Base ◽  
Functional Consequences

scholarly journals NDM-4 Metallo-β-Lactamase with Increased Carbapenemase Activity from Escherichia coli

2012 ◽  
Vol 56 (4) ◽  
pp. 2184-2186 ◽  
Author(s):  
Patrice Nordmann ◽  
Anne E. Boulanger ◽  
Laurent Poirel
Keyword(s):  
Escherichia Coli ◽  
Amino Acid ◽  
Amino Acid Substitution ◽  
Active Sites ◽  
Hydrolytic Activity ◽  
Single Amino Acid Substitution ◽  
Single Amino Acid ◽  
Amino Acid Substitutions ◽  
Content Type

ABSTRACTA clinicalEscherichia coliisolate resistant to all β-lactams, including carbapenems, expressed a novel metallo-β-lactamase (MBL), NDM-4, differing from NDM-1 by a single amino acid substitution (Met154Leu). NDM-4 possessed increased hydrolytic activity toward carbapenems and several cephalosporins compared to that of NDM-1. This amino acid substitution was not located in the known active sites of NDM-1, indicating that remote amino acid substitutions might also play a role in the extended activity of this MBL.

scholarly journals Mutational Analysis of the Escherichia coli melR Gene Suggests a Two-State Concerted Model To Explain Transcriptional Activation and Repression in the Melibiose Operon

2006 ◽  
Vol 188 (9) ◽  
pp. 3199-3207 ◽  
Author(s):  
Christina Kahramanoglou ◽  
Christine L. Webster ◽  
Mohamed Samir el-Robh ◽  
Tamara A. Belyaeva ◽  
Stephen J. W. Busby
Keyword(s):  
Escherichia Coli ◽  
Amino Acid ◽  
Hybrid System ◽  
Transcriptional Activation ◽  
Mutational Analysis ◽  
Single Amino Acid ◽  
Amino Acid Substitutions ◽  
Supporting Evidence ◽  
Conformational States ◽  
Two Hybrid

ABSTRACT Transcription of the Escherichia coli melAB operon is regulated by the MelR protein, an AraC family member whose activity is modulated by the binding of melibiose. In the absence of melibiose, MelR is unable to activate the melAB promoter but autoregulates its own expression by repressing the melR promoter. Melibiose triggers MelR-dependent activation of the melAB promoter and relieves MelR-dependent repression of the melR promoter. Twenty-nine single amino acid substitutions in MelR that result in partial melibiose-independent activation of the melAB promoter have been identified. Combinations of different substitutions result in almost complete melibiose-independent activation of the melAB promoter. MelR carrying each of the single substitutions is less able to repress the melR promoter, while MelR carrying some combinations of substitutions is completely unable to repress the melR promoter. These results argue that different conformational states of MelR are responsible for activation of the melAB promoter and repression of the melR promoter. Supporting evidence for this is provided by the isolation of substitutions in MelR that block melibiose-dependent activation of the melAB promoter while not changing melibiose-independent repression of the melR promoter. Additional experiments with a bacterial two-hybrid system suggest that interactions between MelR subunits differ according to the two conformational states.

scholarly journals Identification of Escherichia coli dnaE(polC) Mutants with Altered Sensitivity to 2′,3′-Dideoxyadenosine

2000 ◽  
Vol 182 (14) ◽  
pp. 3942-3947 ◽  
Author(s):  
Koji Hiratsuka ◽  
Linda J. Reha-Krantz
Keyword(s):  
Escherichia Coli ◽  
Amino Acid ◽  
Dna Polymerase ◽  
Protein Product ◽  
Single Amino Acid ◽  
Amino Acid Substitutions ◽  
Α Subunit ◽  
Nucleotide Interactions ◽  
Increased Sensitivity ◽  
Mutant Phenotypes

ABSTRACT Bacteria with reduced DNA polymerase I activity have increased sensitivity to killing by chain-terminating nucleotides (S. A. Rashbaum and N. R. Cozzarelli, Nature 264:679–680, 1976). We have used this observation as the basis of a genetic strategy to identify mutations in the dnaE (polC) gene ofEscherichia coli that alter sensitivity to 2′,3′-dideoxyadenosine (ddA). Two dnaE (polC) mutant strains with increased sensitivity to ddA and one strain with increased resistance were isolated and characterized. The mutant phenotypes are due to single amino acid substitutions in the α subunit, the protein product of the dnaE (polC) gene. Increased sensitivity to ddA is produced by the L329F and H417Y substitutions, and increased resistance is produced by the G365S substitution. The L329F and H417Y substitutions also reduce the accuracy of DNA replication (the mutator phenotype), while the G365S substitution increases accuracy (the antimutator phenotype). All of the amino acid substitutions are in conserved regions near essential aspartate residues. These results prove the effectiveness of the genetic strategy in identifying informative dnaE(polC) mutations that can be used to elucidate the molecular basis of nucleotide interactions in the α subunit of the DNA polymerase III holoenzyme.

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