Structure reveals regulatory mechanisms of a MaoC-like hydratase from Phytophthora capsici involved in biosynthesis of polyhydroxyalkanoates (PHAs).
BACKGROUND
Polyhydroxyalkanoates (PHAs) have attracted increasing attention as "green plastic" due to their biodegradable, biocompatible, thermoplastic, and mechanical properties, and considerable research has been undertaken to develop low cost/high efficiency processes for the production of PHAs. MaoC-like hydratase (MaoC), which belongs to (R)-hydratase involved in linking the β-oxidation and the PHA biosynthetic pathways, has been identified recently. Understanding the regulatory mechanisms of (R)-hydratase catalysis is critical for efficient production of PHAs that promise synthesis an environment-friendly plastic.


RESULTS
We have determined the crystal structure of a new MaoC recognized from Phytophthora capsici. The crystal structure of the enzyme was solved at 2.00 Å resolution. The structure shows that MaoC has a canonical (R)-hydratase fold with an N-domain and a C-domain. Supporting its dimerization observed in structure, MaoC forms a stable homodimer in solution. Mutations that disrupt the dimeric MaoC result in a complete loss of activity toward crotonyl-CoA, indicating that dimerization is required for the enzymatic activity of MaoC. Importantly, structure comparison reveals that a loop unique to MaoC interacts with an α-helix that harbors the catalytic residues of MaoC. Deletion of the loop enhances the enzymatic activity of MaoC, suggesting its inhibitory role in regulating the activity of MaoC.


CONCLUSIONS
The data in our study reveal the regulatory mechanism of an (R)-hydratase, providing information on enzyme engineering to produce low cost PHAs.
Department of Plant Pathology, Shandong Agricultural University, Tai'an, Shandong, China.
Huizheng
H
Wang
Kai
K
Zhang
Jie
J
Zhu
Weiwei
W
Song
Li
L
Zhao
Xiuguo
X
Zhang
D000214:Acyl Coenzyme A / Q000737:chemistry* / Q000378:metabolism; D000595:Amino Acid Sequence; D001665:Binding Sites; D055162:Biocatalysis; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D004746:Enoyl-CoA Hydratase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010084:Oxidation-Reduction; D010838:Phytophthora / Q000737:chemistry* / Q000201:enzymology; D054813:Polyhydroxyalkanoates / Q000096:biosynthesis*; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D000214:Acyl Coenzyme A; D054813:Polyhydroxyalkanoates; D011994:Recombinant Proteins; C010701:crotonyl-coenzyme A; D004746:Enoyl-CoA Hydratase