Work

Structural Basis for Disparate Sugar-Binding Specificities in the Homologous Cargo Receptors ERGIC-53 and VIP36

Year: 2014

Type: article

Abstract: ERGIC-53 and VIP36 are categorized as leguminous type (L-type) lectins, and they function as cargo receptors for trafficking certain N-linked glycoproteins in the secretory pathway in animal cells. They share structural similarities in their carbohydrate recognition domains (CRDs) but exhibit distinct sugar-binding specificities and affinities. VIP36 specifically interacts with the α1,2-linked D1 mannosyl arm without terminal glucosylation, while ERGIC-53 shows a broader specificity and lower binding affinity to the high-mannose-type oligosaccharides, irrespective of the presence or absence of the non-reducing terminal glucose residue at the D1 arm. In this study, we determined the crystal structure of ERGIC-53-CRD in complex with their binding partner, MCFD2 and the α1,2 mannotriose which corresponds to the trisaccharide of the D1 arm of high-mannose-type glycans. ERGIC-53 can interact with the D1 trimannosyl arm in two alternative modes, one of which is similar but distinct from that previously observed for VIP36. ERGIC-53 has a shallower sugar-binding pocket than VIP36 because of the single amino acid substitution, Asp-to-Gly. This enables ERGIC-53 to accommodate the non-reducing terminal glucose of the D1 arm in its CRD. In the other interaction mode, the 3-OH group of the terminal mannose was situated outward with respect to the sugar binding pocket, also enabling the Glcα1-3 linkage formation without steric hindrance. Our findings thus provide a structural basis for the broad sugar-binding specificity of the ERGIC-53/MCFD2 cargo receptor complex.

Source: PLoS ONE

DOI: 10.1371/journal.pone.0087963

Authors: Tadashi Satoh, Kousuke Suzuki, Takumi Yamaguchi, Koichi Kato

Institutions: Nagoya City University, Japan Science and Technology Agency, National Institutes of Natural Sciences, Okazaki Institute for Integrative Bioscience, Institute for Molecular Science

Language: English

Topic: Glycosylation and Glycoproteins Research

Subfield: Molecular Biology

Field: Biochemistry, Genetics and Molecular Biology

Domain: Life Sciences

Open Access status: gold

Estimated APC paid: $2,382

Funders: Universität Basel, University of Tokyo, High Energy Accelerator Research Organization, Japan Society for the Promotion of Science