Interfacial plasticity facilitates high reaction rate of <i>E. coli</i> FAS malonyl-CoA:ACP transacylase, FabD
Laëtitia Misson, Jeffrey T. Mindrebo, Tony D. Davis, Ashay Patel, J. Andrew McCammon, Joseph P. Noel, Michael D. Burkart
Abstract
FAS AT, FabD, and its cognate ACP, AcpP, to interrogate type II FAS ACP-AT interactions. We utilize a covalent crosslinking probe to trap transient interactions between AcpP and FabD to elucidate the X-ray crystal structure of a type II ACP-AT complex. Our structural data are supported using a combination of mutational, crosslinking, and kinetic analyses, and long-timescale molecular dynamics (MD) simulations. Together, these complementary approaches reveal key catalytic features of FAS ACP-AT interactions. These mechanistic inferences suggest that AcpP adopts multiple, productive conformations at the AT binding interface, allowing the complex to sustain high transacylation rates. Furthermore, MD simulations support rigid body subdomain motions within the FabD structure that may play a key role in AT activity and substrate selectivity.