The crystal structure of UDP-N-acetylmuramate-L-alanine ligase (murC) from Yersinia pestis CO92 in complex with AMP was determined by molecular replacement and refined to 2.25 A resolution. Two chains (1.0 A r.m.s.d. over 458 C-alpha atoms) in the P212121 asymmetric unit do not bury significant surface area to be classified as a dimer according the PISA analysis. Crystal packing did not revealed any reliable oligomers too. Each copy of the protein consists of three domains with each domain represented by a central beta-sheet that is flanked by alpha helices. The N-terminal domain has a parallel 5-stranded beta-sheet, whereas middle and C-terminal domains have antiparallel 10-stranded and 6-stranded, respectively, beta-sheets. The N-terminal domain is the smallest of the three domains. Molecule of adenosine monophosphate is bound at the interface between the middle domain and the C-terminal domain. The electron density of the ligand is well resolved.