The X-ray crystal structures of human alpha-phosphomannomutase 1 reveal the structural basis of congenital disorder of glycosylation type 1a. J Biol Chem 2006 May 26;281(21):14918-26
Date
03/17/2006Pubmed ID
16540464DOI
10.1074/jbc.M601505200Scopus ID
2-s2.0-33744955343 (requires institutional sign-in at Scopus site) 62 CitationsAbstract
Congenital 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.
Author List
Silvaggi NR, Zhang C, Lu Z, Dai J, Dunaway-Mariano D, Allen KNAuthor
Nicholas R. Silvaggi PhD Assistant Professor in the Chemistry and Biochemistry department at University of Wisconsin - MilwaukeeMESH terms used to index this publication - Major topics in bold
Amino Acid SequenceAspartic Acid
Carbohydrate Metabolism, Inborn Errors
Cloning, Molecular
Crystallography, X-Ray
Humans
Hydrolases
Magnesium
Models, Chemical
Models, Molecular
Molecular Conformation
Molecular Sequence Data
Phosphotransferases (Phosphomutases)
Protein Isoforms