2fue
Human alpha-Phosphomannomutase 1 with D-mannose 1-phosphate and Mg2+ cofactor bound
Structural highlights
FunctionPMM1_HUMAN Involved in the synthesis of the GDP-mannose and dolichol-phosphate-mannose required for a number of critical mannosyl transfer reactions. In addition, may be responsible for the degradation of glucose-1,6-bisphosphate in ischemic brain. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedCongenital disorder of glycosylation type 1a (CDG-1a) is a congenital disease characterized by severe defects in nervous system development. It is caused by mutations in alpha-phosphomannomutase (of which there are two isozymes, alpha-PMM1 and alpha-PPM2). Here we report the x-ray crystal structures of human alpha-PMM1 in the open conformation, with and without the bound substrate, alpha-D-mannose 1-phosphate. Alpha-PMM1, like most haloalkanoic acid dehalogenase superfamily (HADSF) members, consists of two domains, the cap and core, which open to bind substrate and then close to provide a solvent-exclusive environment for catalysis. The substrate phosphate group is observed at a positively charged site of the cap domain, rather than at the core domain phosphoryl-transfer site defined by the Asp(19) nucleophile and Mg(2+) cofactor. This suggests that substrate binds first to the cap and then is swept into the active site upon cap closure. The orientation of the acid/base residue Asp(21) suggests that alpha-phosphomannomutase (alpha-PMM) uses a different method of protecting the aspartylphosphate from hydrolysis than the HADSF member beta-phosphoglucomutase. It is hypothesized that the electrostatic repulsion of positive charges at the interface of the cap and core domains stabilizes alpha-PMM1 in the open conformation and that the negatively charged substrate binds to the cap, thereby facilitating its closure over the core domain. The two isozymes, alpha-PMM1 and alpha-PMM2, are shown to have a conserved active-site structure and to display similar kinetic properties. Analysis of the known mutation sites in the context of the structures reveals the genotype-phenotype relationship underlying CDG-1a. The X-ray crystal structures of human alpha-phosphomannomutase 1 reveal the structural basis of congenital disorder of glycosylation type 1a.,Silvaggi NR, Zhang C, Lu Z, Dai J, Dunaway-Mariano D, Allen KN J Biol Chem. 2006 May 26;281(21):14918-26. Epub 2006 Mar 15. PMID:16540464[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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