Interdomain disulfide bridge in the rice granule bound starch synthase I catalytic domain as elucidated by X-ray
1Biomolecular Research Unit, National Institute of Agrobiological Sciences, 2-1-2 Kannondai, Tsukuba, Ibaraki 305-8602, Japan. momma@affrc.go.jp
Abstract:
The catalytic domain of rice (Oryza sativa japonica) granule bound starch synthase I (OsGBSSI-CD) was overexpressed and the three-dimensional structures of the ligand-free and ADP-bound forms were determined. The structures were similar to those reported for bacterial and archaeal glycogen synthases, which belong to glycosyltransferase family 5. They had Rossmann fold N- and C-domains connected by canonical two-hinge peptides, and an interdomain disulfide bond that appears to be conserved in the Poaceae plant family. The presence of three covalent linkages might explain why both OsGBSSI-CD structures adopted only the closed domain arrangement.
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