Functional Demonstration of Reverse Transsulfuration in the Mycobacterium tuberculosis Complex Reveals That Methionine Is the Preferred Sulfur Source for Pathogenic Mycobacteria
| Autor: | N. G. Coldham, R. Glyn Hewinson, Esen Wooff, Lisa Keating, Tanya Parish, Paul R. Wheeler, Stephen V. Gordon |
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| Rok vydání: | 2005 |
| Předmět: |
Time Factors
Auxotrophy DNA Mutational Analysis Transsulfuration Disaccharides Biochemistry chemistry.chemical_compound Methionine Methionine synthase Amino Acids Cloning Molecular Chromatography High Pressure Liquid Genome Glycopeptides Mycobacterium bovis Sulfate transport Alkynes Plasmids Ultraviolet Rays Carbon-Oxygen Lyases Glycine Biology Escherichia coli Homoserine Cysteine Sulfhydryl Compounds Molecular Biology Ions Cell-Free System Genetic Complementation Test Cystathionine gamma-Lyase Biological Transport Mycobacterium tuberculosis Cell Biology Cystathionine beta synthase Protein Structure Tertiary Mycothiol Kinetics Models Chemical chemistry Mutation biology.protein Pyrazoles Ultracentrifugation Genome Bacterial Inositol Sulfur |
| Zdroj: | Journal of Biological Chemistry. 280:8069-8078 |
| ISSN: | 0021-9258 |
| Popis: | Methionine can be used as the sole sulfur source by the Mycobacterium tuberculosis complex although it is not obvious from examination of the genome annotation how these bacteria utilize methionine. Given that genome annotation is a largely predictive process, key challenges are to validate these predictions and to fill in gaps for known functions for which genes have not been annotated. We have addressed these issues by functional analysis of methionine metabolism. Transport, followed by metabolism of (35)S methionine into the cysteine adduct mycothiol, demonstrated the conversion of exogenous methionine to cysteine. Mutational analysis and cloning of the Rv1079 gene showed it to encode the key enzyme required for this conversion, cystathionine gamma-lyase (CGL). Rv1079, annotated metB, was predicted to encode cystathionine gamma-synthase (CGS), but demonstration of a gamma-elimination reaction with cystathionine as well as the gamma-replacement reaction yielding cystathionine showed it encodes a bifunctional CGL/CGS enzyme. Consistent with this, a Rv1079 mutant could not incorporate sulfur from methionine into cysteine, while a cysA mutant lacking sulfate transport and a methionine auxotroph was hypersensitive to the CGL inhibitor propargylglycine. Thus, reverse transsulfuration alone, without any sulfur recycling reactions, allows M. tuberculosis to use methionine as the sole sulfur source. Intracellular cysteine was undetectable so only the CGL reaction occurs in intact mycobacteria. Cysteine desulfhydrase, an activity we showed to be separable from CGL/CGS, may have a role in removing excess cysteine and could explain the ability of M. tuberculosis to recycle sulfur from cysteine, but not methionine. |
| Databáze: | OpenAIRE |
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