TY - JOUR T1 - Gating Mechanism of β-Ketoacyl-ACP Synthases JF - bioRxiv DO - 10.1101/644518 SP - 644518 AU - Jeffrey T. Mindrebo AU - Ashay Patel AU - Woojoo E. Kim AU - Tony D. Davis AU - Aochiu Chen AU - Thomas G. Bartholow AU - James J. La Clair AU - J. Andrew McCammon AU - Joseph P. Noel AU - Michael D. Burkart Y1 - 2019/01/01 UR - http://biorxiv.org/content/early/2019/05/21/644518.abstract N2 - Formation of carbon-carbon bonds via β-ketoacyl-acyl carrier protein (ACP) synthases (KS), are key reactions during de novo fatty acid and polyketide biosynthesis. KSs recognize multiple ACPs and choreograph ping-pong mechanisms often in an iterative fashion. Therefore, KSs must limit non-productive protein-protein interactions (PPIs) to achieve high degrees of reaction fidelity. To better understand the stereochemical features governing substrate discrimination during ACP•KS PPIs, we determined x-ray crystal structures complemented by molecular dynamic simulations of E. coli AcpP in complex with the elongating KSs, FabF and FabB. Covalently trapped substrate analogs were used to interrogate critical catalytic events accompanying carbon-carbon bond formation revealing a previously unknown gating mechanism during the binding and delivery of acyl-AcpPs. Two active site loops undergo large conformational excursions during this dynamic gating mechanism and are likely evolutionarily conserved features generally in elongating KSs. ER -