Title: Crystal structure of Ralstonia eutrophapolyhydroxyalkanoate synthase C-terminal domain and reaction mechanisms

Author: Kim, J.E., Kim, Y-J., Choi, S.Y., Lee, S.Y.,Kim, K-J.

Journal: Biotechnol. J., 12(1):  1-12(2017. 1)

Abstract:

Polyhydroxyalkanoates(PHAs) are natural polyesters synthesized by numerous microorganisms as energyand reducing power storage materials, and have attracted much attention assubstitutes for petroleum-based plastics. Here, we report the first crystalstructure of Ralstonia eutropha PHA synthase at 1.8 Å resolution and structure-based mechanisms for PHApolymerization. RePhaC1 contains two distinct domains, the N-terminal (RePhaC1_ND)and C-terminal domains (RePhaC1_CD), and exists as a dimer. RePhaC1_CDcatalyzes polymerization via non-processive ping-pong mechanism using aCys-His-Asp catalytic triad. Molecular docking simulation of3-hydroxybutyryl-CoA to the active site of RePhaC1_CD revealsresidues involved in the formation of 3-hydroxybutyryl-CoA binding pocket andsubstrate binding tunnel. Comparative analysis with other polymeraseselucidates how different classes of PHA synthases show different substratespecificities. Furthermore, we attempted structure-based protein engineeringand developed a RePhaC1 mutant with enhanced PHA synthase activity.