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Structure-based site-directed mutagenesis of the UDP-MurNAc-pentapeptide-binding cavity of the FemX alanyl transferase from Weissella viridescens.

ABSTRACT: Weissella viridescens FemX (FemX(Wv)) belongs to the Fem family of nonribosomal peptidyl transferases that use aminoacyl-tRNA as the amino acid donor to synthesize the peptide cross-bridge found in the peptidoglycan of many species of pathogenic gram-positive bacteria. We have recently solved the crystal structure of FemX(Wv) in complex with the peptidoglycan precursor UDP-MurNAc-pentapeptide and report here the site-directed mutagenesis of nine residues located in the binding cavity for this substrate. Two substitutions, Lys36Met and Arg211Met, depressed FemX(Wv) transferase activity below detectable levels without affecting protein folding. Analogues of UDP-MurNAc-pentapeptide lacking the phosphate groups or the C-terminal D-alanyl residues were not substrates of the enzyme. These results indicate that Lys36 and Arg211 participate in a complex hydrogen bond network that connects the C-terminal D-Ala residues to the phosphate groups of UDP-MurNAc-pentapeptide and constrains the substrate in a conformation that is essential for transferase activity.

SUBMITTER: Maillard AP

PROVIDER: S-EPMC1112068 | biostudies-literature | 2005 Jun

REPOSITORIES: biostudies-literature

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Structure-based site-directed mutagenesis of the UDP-MurNAc-pentapeptide-binding cavity of the FemX alanyl transferase from Weissella viridescens.

Maillard Antoine P AP Biarrotte-Sorin Sabrina S Villet Régis R Mesnage Stéphane S Bouhss Ahmed A Sougakoff Wladimir W Mayer Claudine C Arthur Michel M

Journal of bacteriology 20050601 11

Weissella viridescens FemX (FemX(Wv)) belongs to the Fem family of nonribosomal peptidyl transferases that use aminoacyl-tRNA as the amino acid donor to synthesize the peptide cross-bridge found in the peptidoglycan of many species of pathogenic gram-positive bacteria. We have recently solved the crystal structure of FemX(Wv) in complex with the peptidoglycan precursor UDP-MurNAc-pentapeptide and report here the site-directed mutagenesis of nine residues located in the binding cavity for this su ...[more]

PMID: 15901708

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Project description:Glutathione transferase (GST) epsilon (also known as GST2 or GST B1B1), the major Class Alpha GST in human liver has been subjected to oligonucleotide-directed site-specific mutagenesis. Four arginine residues, R13, R20, R69 and R187, of which all but R69 are strictly conserved through GST Classes Alpha, Mu and Pi have been replaced by Ala. The mutant enzymes have been expressed in Escherichia coli, purified by affinity chromatography and characterised. Compared with the wild-type enzyme, all mutant GSTs had altered catalytic properties. All mutants had decreased specific activity with 1-chloro-2,4-dinitrobenzene (CDNB). Mutants R13A, R69A and R187A also showed decreased activities with other substrates such as cumene hydroperoxide (CuOOH) and androstenedione. In contrast, mutant R20A had an increased peroxidase activity and an isomerase activity essentially the same as that of the wild-type GST. With the substrates used, kcat./Km values were decreased for all mutant GSTs. Increases in the [S0.5] values were most significant for glutathione (GSH), while values for CDNB and CuOOH were less markedly affected. Thus, various kinetic data indicate that the GSH affinity has been reduced by the mutations and that this loss of affinity is linked to the decreased specific activities. Inhibition studies showed an increased sensitivity towards S-hexyl-GSH; this was particularly marked for mutant R69A. Mutant R20A had a lowered [I50] value but, in contrast, also the highest [I80] value as compared with the wild-type enzyme. Towards bromosulphophthalein, mutants R20A and R69A had a markedly increased sensitivity, about 35-fold in comparison with the wild-type. The inhibition properties of mutant R187A were similar to those of the wild-type enzyme and the properties of mutant R13A were in between. The increased sensitivity to S-hexyl-GSH, in contrast with the decreased affinity for GSH, was suggested to be due to an altered distribution between conformational states of the enzyme induced by the mutations. The arginine residues in positions 13, 20 and 69 all seem to be important for the catalytic properties of GST. Further, the inhibition studies indicate a role of arginine residues in the stabilisation of conformational states of the enzyme.

Dataset Information

Structure-based site-directed mutagenesis of the UDP-MurNAc-pentapeptide-binding cavity of the FemX alanyl transferase from Weissella viridescens.

Publications

Structure-based site-directed mutagenesis of the UDP-MurNAc-pentapeptide-binding cavity of the FemX alanyl transferase from Weissella viridescens.

Similar Datasets

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