Crystal structure of Ralstonia eutropha polyhydroxyalkanoate synthase C-terminal domain and reaction mechanisms

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• 作者：Jieun Kim ; Yeo-Jin Kim ; So Young Choi ; Sang Yup Lee and Kyung-Jin Kim
• 刊名：Biotechnology Journal
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：12
• 期：1
• 全文大小：4149K
• ISSN：1860-7314

文摘

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