MgF3− and α-Galactose 1-Phosphate in the Active Site of β-Phosphoglucomutase Form a Transition State Analogue of Phosphoryl Transfer

详细信息    查看全文

• 作者：Nicola J. Baxter ; Andrea M. Hounslow ; Matthew W. Bowler ; Nicholas H. Williams ; G. Michael Blackburn ; Jonathan P. Waltho
• 刊名：Journal of the American Chemical Society
• 出版年：2009
• 出版时间：November 18, 2009
• 年：2009
• 卷：131
• 期：45
• 页码：16334-16335
• 全文大小：131K
• 年卷期：v.131,no.45(November 18, 2009)
• ISSN：1520-5126

文摘

¹⁹F-based NMR analysis and hydrogen/deuterium primary isotope shifts establish the formation of a highly populated solution-state trigonal bipyramidal complex involving β-phosphoglucomutase (β-PGM), α-galactose 1-phosphate (αGal1P), and trifluoromagnesate (MgF₃⁻), PGM-MgF₃-αGal1P, that is a transition state analogue for phosphoryl transfer. Full backbone resonance assignment of the protein shows that its structure is in the closed conformation required for catalytic activity and is closely related to the corresponding complex with glucose 6-phosphate, which we have recently identified using NMR analysis in solution and X-ray crystallography in the solid state. The previous identification of three structural waters in a PGM-αGal1P binary substrate complex had indicated that, in the presence of αGal1P, magnesium ions, and fluoride, β-PGM should indeed form a PGM-MgF₃-αGal1P-TSA complex whereas, in the solid-state, apparently it did not. This cast doubt on the validity of the interpretation of MgF₃⁻ complexes. The present work establishes that, in solution, the expectation that a PGM-MgF₃-αGal1P-TSA complex should readily form is fulfilled. These results thus refute the final evidence used to claim that the trigonal bipyramidal species observed in some solid-state structures of complexes involving β-PGM are pentaoxyphosphorane intermediates.