Structure of the MUR1 GDP-Mannose 4,6-Dehydratase from Arabidopsis thaliana: Implications for Ligand Binding and Specificity
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- 作者：Anne M. Mulichak ; Christopher P. Bonin ; Wolf-Dieter Reiter ; and R. Michael Garavito
- 刊名：Biochemistry
- 出版年：2002
- 出版时间：December 31, 2002
- 年：2002
- 卷：41
- 期：52
- 页码：15578 - 15589
- 全文大小：901K
- 年卷期：v.41,no.52(December 31, 2002)
- ISSN：1520-4995
文摘
GDP-D-mannose 4,6-dehydratase catalyzes the first step in the de novo synthesis of GDP-L-fucose, the activated form of L-fucose, which is a component of glycoconjugates in plants known to beimportant to the development and strength of stem tissues. We have determined the three-dimensionalstructure of the MUR1 dehydratase isoform from Arabidopsis thaliana complexed with its NADPH cofactoras well as with the ligands GDP and GDP-D-rhamnose. MUR1 is a member of the nucleoside-diphosphosugar modifying subclass of the short-chain dehydrogenase/reductase enzyme family, havinghomologous structures and a conserved catalytic triad of Lys, Tyr, and Ser/Thr residues. MUR1 is thefirst member of this subfamily to be observed as a tetramer, the interface of which reveals a close andintimate overlap of neighboring NADP+-binding sites. The GDP moiety of the substrate also binds in anunusual syn conformation. The protein-ligand interactions around the hexose moiety of the substratesupport the importance of the conserved triad residues and an additional Glu side chain serving as ageneral base for catalysis. Phe and Arg side chains close to the hexose ring may serve to confer substratespecificity at the O2 position. In the MUR1/GDP-D-rhamnose complex, a single unique monomer withinthe protein tetramer that has an unoccupied substrate site highlights the conformational changes thataccompany substrate binding and may suggest the existence of negative cooperativity in MUR1 function.