FIG. 2.

Ceftazidime covalently bound to Ser-64 of the superposed structures of CMY-2 and CMY-30. Ceftazidime has been modeled in a catalytically competent conformation similar to that adopted by loracarbef (see text). The view is focused on the possible steric constraints between the aminothiazole substituent of ceftazidime and the Ω loop residues 211 and 221. Calculated distances between N19-CMY2-Val211 Cγ2 (2.3 Å) and S16-CMY2-Tyr221 Cδ1 (2.5 Å) are shown by purple dashed lines. Green dashed lines indicate distances between N19-CMY30-Gly211 Cα (3.4 Å) and S16-CMY30-Tyr221 Cδ1 (2.7 Å). Carbon atoms of CMY-2 residues are colored orange, and those of CMY-30 are colored green. Ceftazidime and Ser64 carbon atoms are colored magenta.