Crystal structure and enantiomer selection by D-alanyl carrier protein ligase DltA from Bacillus cereus.
Ubiquitous D-alanylation of lipoteichoic acids modulates the surface charge and ligand binding of the gram-positive cell wall. Disruption of the bacterial DltABCD gene involved in teichoic acid alanylation, as well as inhibition of the DltA protein, has been shown to increase a gram-positive bacterium's susceptibility to antibiotics. The DltA D-alanyl carrier protein ligase promotes a two-step process starting with adenylation of D-alanine. We have determined the 2.0 A resolution crystal structure of a DltA protein from Bacillus cereus in complex with the D-alanine adenylate intermediate of the first reaction. Despite the low level of sequence similarity, the DltA structure resembles known structures of adenylation domains such as the acetyl-CoA synthetase. The enantiomer selection appears to be enhanced by the medium-sized side chain of Cys-269. The Ala-269 mutant protein shows marked loss of such selection. The network of noncovalent interactions between the D-alanine adenylate and DltA provides structure-based rationale for aiding the design of tight-binding DltA inhibitors for combating infectious gram-positive bacteria such as the notorious methicillin-resistant Staphylococcus aureus.
Department of Biochemistry, University of Saskatchewan, A3 Health Sciences Building, 107 Wiggins Road, Saskatoon, Saskatchewan, Canada S7N 5E5.
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D000409:Alanine / Q000737:chemistry; D000595:Amino Acid Sequence; D001409:Bacillus cereus / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D019729:Carbon-Oxygen Ligases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D004269:DNA, Bacterial / Q000235:genetics; D005798:Genes, Bacterial; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013237:Stereoisomerism; D013379:Substrate Specificity
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D011994:Recombinant Proteins; D019729:Carbon-Oxygen Ligases; C502532:DltA protein, Bacillus subtilis; D000409:Alanine