Figure 1. Active site interactions of Acs.
The structure of the wild-type Acs enzyme determined in the presence of propyl-AMP and CoA (1PG4) and amino acids that form the active site pocket are shown. A. The orientation of propyl-AMP bound to Acs in the thioester-forming conformation illustrates residues that interact that interact with the nucleotide. Interactions made to the nucleotide include Arg526 and Arg515, which interact with the phosphate group. The acetate binding pocket is formed by the three side chains of Val310, Val386, and Trp414 (shown in green). B. The CoA binding site. The nucleotide of CoA binds at the surface of the protein and the pantetheine group leads in to the adenylate site through a tunnel that is bordered by Ala357 and Gly524, two residues that were mutated to contain bulkier side chains. Arg584 was positioned to interact with the CoA 3' phosphate. Arg194 was oriented away from the phosphate but could interact through a torsional rotation.