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Structural and biochemical analyses of alanine racemase from the multidrug-resistant Clostridium difficile strain 630.

ABSTRACT: Clostridium difficile, a Gram-positive, spore-forming anaerobic bacterium, is the leading cause of infectious diarrhea among hospitalized patients. C. difficile is frequently associated with antibiotic treatment, and causes diseases ranging from antibiotic-associated diarrhea to life-threatening pseudomembranous colitis. The severity of C. difficile infections is exacerbated by the emergence of hypervirulent and multidrug-resistant strains, which are difficult to treat and are often associated with increased mortality rates. Alanine racemase (Alr) is a pyridoxal-5'-phosphate (PLP)-dependent enzyme that catalyzes the reversible racemization of L- and D-alanine. Since D-alanine is an essential component of the bacterial cell-wall peptidoglycan, and there are no known Alr homologs in humans, this enzyme is being tested as an antibiotic target. Cycloserine is an antibiotic that inhibits Alr. In this study, the catalytic properties and crystal structures of recombinant Alr from the virulent and multidrug-resistant C. difficile strain 630 are presented. Three crystal structures of C. difficile Alr (CdAlr), corresponding to the complex with PLP, the complex with cycloserine and a K271T mutant form of the enzyme with bound PLP, are presented. The structures are prototypical Alr homodimers with two active sites in which the cofactor PLP and cycloserine are localized. Kinetic analyses reveal that the K271T mutant CdAlr has the highest catalytic constants reported to date for any Alr. Additional studies are needed to identify the basis for the high catalytic activity. The structural and activity data presented are first steps towards using CdAlr for the development of structure-based therapeutics for C. difficile infections.

SUBMITTER: Asojo OA

PROVIDER: S-EPMC4089486 | biostudies-literature | 2014 Jul

REPOSITORIES: biostudies-literature

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Structural and biochemical analyses of alanine racemase from the multidrug-resistant Clostridium difficile strain 630.

Asojo Oluwatoyin A OA Nelson Sarah K SK Mootien Sara S Lee Yashang Y Rezende Wanderson C WC Hyman Daniel A DA Matsumoto Monica M MM Reiling Scott S Kelleher Alan A Ledizet Michel M Koski Raymond A RA Anthony Karen G KG

Acta crystallographica. Section D, Biological crystallography 20140629 Pt 7

Clostridium difficile, a Gram-positive, spore-forming anaerobic bacterium, is the leading cause of infectious diarrhea among hospitalized patients. C. difficile is frequently associated with antibiotic treatment, and causes diseases ranging from antibiotic-associated diarrhea to life-threatening pseudomembranous colitis. The severity of C. difficile infections is exacerbated by the emergence of hypervirulent and multidrug-resistant strains, which are difficult to treat and are often associated w ...[more]

PMID: 25004969

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Project description:Clostridium difficile is a gram-positive, spore-forming enteric anaerobe which can infect humans and a wide variety of animal species. Recently, the incidence and severity of human C. difficile infection has markedly increased. In this study, we evaluated the genomic content of 73 C. difficile strains isolated from humans, horses, cattle, and pigs by comparative genomic hybridization with microarrays containing coding sequences from C. difficile strains 630 and QCD-32g58. The sequenced genome of C. difficile strain 630 was used as a reference to define a candidate core genome of C. difficile and to explore correlations between host origins and genetic diversity. Approximately 16% of the genes in strain 630 were highly conserved among all strains, representing the core complement of functional genes defining C. difficile. Absent or divergent genes in the tested strains were distributed across the entire C. difficile 630 genome and across all the predicted functional categories. Interestingly, certain genes were conserved among strains from a specific host species, but divergent in isolates with other host origins. This information provides insight into the genomic changes which might contribute to host adaptation. Due to a high degree of divergence among C. difficile strains, a core gene list from this study offers the first step toward the construction of diagnostic arrays for C. difficile.investigated by determining changes in transcript profiles when aerobic steady-state cultures were depleted of air. Dye-swap experiments with genomic DNA of tested and reference strains 8383cy3.gpr- Cy3 – test, Cy5 – reference 8384cy3.gpr- Cy3 – test, Cy5 – reference 8384cy5.gpr- Cy3 – reference, Cy5 – test 8385cy3.gpr- Cy3 – test, Cy5 – reference 8385cy5.gpr- Cy3 – reference, Cy5 – test 8386cy3.gpr- Cy3 – test, Cy5 – reference 8525cy3.gpr- Cy3 – test, Cy5 – reference 8525cy5.gpr- Cy3 – reference, Cy5 – test 8527cy5.gpr- Cy3 – reference, Cy5 – test 8529cy5.gpr- Cy3 – reference, Cy5 – test 8531cy3.gpr- Cy3 – test, Cy5 – reference 8531cy5.gpr- Cy3 – reference, Cy5 – test 8533cy3.gpr- Cy3 – test, Cy5 – reference 8533cy5.gpr- Cy3 – reference, Cy5 – test 8596cy3.gpr- Cy3 – test, Cy5 – reference 8596cy5.gpr- Cy3 – reference, Cy5 – test 8694cy3.gpr- Cy3 – test, Cy5 – reference 8694cy5.gpr- Cy3 – reference, Cy5 – test 2 GPR files per Sample record except for 4 Sample records (GSM480414, GSM480417, GSM480419, and GSM480420) which have 1 GPR file each 4 GPR file for those Sample records are lost

Project description:Clostridioides (Clostridium) difficile is an opportunistic pathogen known for its ability to colonize the human gut under conditions of dysbiosis. Several aspects of its carbon and amino acid metabolism have been investigated, but its cobamide (vitamin B12 and related cofactors) metabolism remains largely unexplored. C. difficile has seven predicted cobamide-dependent pathways encoded in its genome in addition to a nearly complete cobamide biosynthesis pathway and a cobamide uptake system. To address the importance of cobamides to C. difficile, we studied C. difficile 630 Δerm and mutant derivatives under cobamide-dependent conditions in vitro Our results show that C. difficile can use a surprisingly diverse array of cobamides for methionine and deoxyribonucleotide synthesis and can use alternative metabolites or enzymes, respectively, to bypass these cobamide-dependent processes. C. difficile 630 Δerm produces the cobamide pseudocobalamin when provided the early precursor 5-aminolevulinic acid or the late intermediate cobinamide (Cbi) and produces other cobamides if provided an alternative lower ligand. The ability of C. difficile 630 Δerm to take up cobamides and Cbi at micromolar or lower concentrations requires the transporter BtuFCD. Genomic analysis revealed genetic variations in the btuFCD loci of different C. difficile strains, which may result in differences in the ability to take up cobamides and Cbi. These results together demonstrate that, like other aspects of its physiology, cobamide metabolism in C. difficile is versatile.IMPORTANCE The ability of the opportunistic pathogen Clostridioides difficile to cause disease is closely linked to its propensity to adapt to conditions created by dysbiosis of the human gut microbiota. The cobamide (vitamin B12) metabolism of C. difficile has been underexplored, although it has seven metabolic pathways that are predicted to require cobamide-dependent enzymes. Here, we show that C. difficile cobamide metabolism is versatile, as it can use a surprisingly wide variety of cobamides and has alternative functions that can bypass some of its cobamide requirements. Furthermore, C. difficile does not synthesize cobamides de novo but produces them when given cobamide precursors. A better understanding of C. difficile cobamide metabolism may lead to new strategies to treat and prevent C. difficile-associated disease.

Dataset Information

Structural and biochemical analyses of alanine racemase from the multidrug-resistant Clostridium difficile strain 630.

Publications

Structural and biochemical analyses of alanine racemase from the multidrug-resistant Clostridium difficile strain 630.

Similar Datasets

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