Understanding the Role of Histidine in the GHSxG Acyltransferase Active Site Motif: Evidence for Histidine Stabilization of the Malonyl-Enzyme Intermediate

• DOI: 10.1371/journal.pone.0109421
• Publication Date: 2014-10-06T13:53:16Z
• Authors: Sean Poust; Isu Yoon; Paul D. Adams; Leonard Katz; Christopher J. Pe...; Jay D. Keasling
• Keywords: Acyltransferases; Acyltransferases; Alanine

Acyltransferases determine which extender units are incorporated into polyketide and fatty acid products. The ping-pong acyltransferase mechanism utilizes a serine in conserved GHSxG motif. However, the role of histidine this motif is poorly understood. We observed that to alanine mutation (H640A) malonyl-CoA specific yersiniabactin results an approximately seven-fold higher hydrolysis rate over wildtype enzyme, while retaining transacylation activity. propose two possibilities for reduction rate: either H640 structurally stabilizes protein by hydrogen bonding with asparagine ferredoxin-like subdomain protein, or water-mediated bond between malonyl moiety malonyl-O-AT ester intermediate.