Structure of the Lectin Mannose 6-Phosphate Receptor Homology (MRH) Domain of Glucosidase II, an Enzyme That Regulates Glycoprotein Folding Quality Control in the Endoplasmic Reticulum

• Published in: The Journal of biological chemistry 2013-06, Vol.288 (23), p.16460-16475
• Main Authors: Olson, Linda J., Orsi, Ramiro, Alculumbre, Solana G., Peterson, Francis C., Stigliano, Ivan D., Parodi, Armando J., D'Alessio, Cecilia, Dahms, Nancy M.
• Format: Article
• Language: English
• Subjects: alpha-Glucosidases - chemistry; alpha-Glucosidases - genetics; alpha-Glucosidases - metabolism; Crystallography, X-Ray; Endoplasmic Reticulum (ER); Endoplasmic Reticulum - chemistry; Endoplasmic Reticulum - genetics; Endoplasmic Reticulum - metabolism; Glucosidase II β; Glycobiology; Glycobiology and Extracellular Matrices; Glycoprotein; Glycoproteins - chemistry; Glycoproteins - genetics; Glycoproteins - metabolism; Mannose - chemistry; Mannose - genetics; Mannose - metabolism; MRH Domain; N-Glycan; NMR; Protein Folding; Protein Structure, Secondary; Protein Structure, Tertiary; Schizosaccharomyces - enzymology; Schizosaccharomyces - genetics; Schizosaccharomyces pombe Proteins - chemistry; Schizosaccharomyces pombe Proteins - genetics; Schizosaccharomyces pombe Proteins - metabolism; Structural Biology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M113.450239

Here we report for the first time the three-dimensional structure of a mannose 6-phosphate receptor homology (MRH) domain present in a protein with enzymatic activity, glucosidase II (GII). GII is involved in glycoprotein folding in the endoplasmic reticulum. GII removes the two innermost glucose residues from the Glc3Man9GlcNAc2 transferred to nascent proteins and the glucose added by UDP-Glc:glycoprotein glucosyltransferase. GII is composed of a catalytic GIIα subunit and a regulatory GIIβ subunit. GIIβ participates in the endoplasmic reticulum localization of GIIα and mediates in vivo enhancement of N-glycan trimming by GII through its C-terminal MRH domain. We determined the structure of a functional GIIβ MRH domain by NMR spectroscopy. It adopts a β-barrel fold similar to that of other MRH domains, but its binding pocket is the most shallow known to date as it accommodates a single mannose residue. In addition, we identified a conserved residue outside the binding pocket (Trp-409) present in GIIβ but not in other MRHs that influences GII glucose trimming activity. Background: Glucosidase II is an endoplasmic reticulum enzyme involved in quality control of glycoprotein folding. Results: The structure of the lectin domain of GII was determined by NMR spectroscopy. Conclusion: GII lectin domain structure contains a unique Trp residue critical for GII activity. Significance: GIIβ MRH domain structure is the first determined of an MRH domain present in a protein with enzymatic activity.