Figure 3: The active site structure of Vibrio cholerae ASADH with bound NADP and the covalent inactivator SMCS (shown in green). Cys134 is the active site nucleophile, and His274 is the acid-base catalyst. Glu240 and Arg267 are substrate binding groups, with Arg101 and Lys243 comprising part of the phosphate binding site that is occupied in this structure by a water molecule (W2). H. influenzae numbering is in parentheses (figure adapted from reference [16]).