Crystal structure of Bacillus cereus D-alanyl carrier protein ligase (DltA) in complex with ATP.
D-alanylation of lipoteichoic acids modulates the surface charge and ligand binding of the Gram-positive cell wall. Disruption of the bacterial dlt operon involved in teichoic acid alanylation, as well as inhibition of the DltA (D-alanyl carrier protein ligase) protein, has been shown to render the bacterium more susceptible to conventional antibiotics and host defense responses. The DltA catalyzes the adenylation and thiolation reactions of d-alanine. This enzyme belongs to a superfamily of AMP-forming domains such as the ubiquitous acetyl-coenzyme A synthetase. We have determined the 1.9-A-resolution crystal structure of a DltA protein from Bacillus cereus in complex with ATP. This structure sheds light on the geometry of the bound ATP. The invariant catalytic residue Lys492 appears to be mobile, suggesting a molecular mechanism of catalysis for this superfamily of enzymes. Specific roles are also revealed for two other invariant residues: the divalent cation-stabilizing Glu298 and the beta-phosphate-interacting Arg397. Mutant proteins with a glutamine substitution at position 298 or 397 are inactive.
Osman
Khan Tanjid
KT
Department of Biochemistry, University of Saskatchewan, A3 Health Sciences Building, 107 Wiggins Road, Saskatoon, Saskatchewan, Canada S7N 5E5.
Du
Liqin
L
He
Yujiong
Y
Luo
Yu
Y