TABLE 4.

Conserved residues in 145 subclass A1 β-lactamases from Gram-negative bacteria

^aAmino acid position.

^bCS, ABL consensus (96); ILMV, isoleucine (I), leucine (L), methionine (M), and valine (V). Residues in boldface type are considered to be involved in the catalytic mechanism and/or in substrate binding. Shaded residues correspond to originally identified conserved residues (12).