Probing the substrate specificity of Golgi alpha-mannosidase II by use of synthetic oligosaccharides and a catalytic nucleophile mutant.

ABSTRACT: Inhibition of Golgi alpha-mannosidase II (GMII), which acts late in the N-glycan processing pathway, provides a route to blocking cancer-induced changes in cell surface oligosaccharide structures. To probe the substrate requirements of GMII, oligosaccharides were synthesized that contained an alpha(1,3)- or alpha(1,6)-linked 1-thiomannoside. Surprisingly, these oligosaccharides were not observed in X-ray crystal structures of native Drosophila GMII (dGMII). However, a mutant enzyme in which the catalytic nucleophilic aspartate was changed to alanine (D204A) allowed visualization of soaked oligosaccharides and led to the identification of the binding site for the alpha(1,3)-linked mannoside of the natural substrate. These studies also indicate that the conformational change of the bound man

SUBMITTER: Zhong W 

PROVIDER: S-EPMC3982601 | biostudies-literature | 2008 Jul

REPOSITORIES: biostudies-literature