Structural Basis for Recognition of High Mannose Type Glycoproteins by Mammalian Transport Lectin VIP36

Tadashi Satoh,Nathan P Cowieson,Wataru Hakamata,Hiroko Ideo,Keiko Fukushima,Masaaki Kurihara,Ryuichi Kato,Katsuko Yamashita,Soichi Wakatsuki

doi:10.1074/jbc.m703064200

Abstract

VIP36 functions as a transport lectin for trafficking certain high mannose type glycoproteins in the secretory pathway. Here we report the crystal structure of VIP36 exoplasmic/luminal domain comprising a carbohydrate recognition domain and a stalk domain. The structures of VIP36 in complex with Ca(2+) and mannosyl ligands are also described. The carbohydrate recognition domain is composed of a 17-stranded antiparallel beta-sandwich and binds one Ca(2+) adjoining the carbohydrate-binding site. The structure reveals that a coordinated Ca(2+) ion orients the side chains of Asp(131), Asn(166), and His(190) for carbohydrate binding. This result explains the Ca(2+)-dependent carbohydrate binding of this protein. The Man-alpha-1,2-Man-alpha-1,2-Man, which corresponds to the D1 arm of high mannose type glycan, is recognized by eight residues through extensive hydrogen bonds. The complex structures reveal the structural basis for high mannose type glycoprotein recognition by VIP36 in a Ca(2+)-dependent and D1 arm-specific manner.

Highlights

VIP36, vesicular-integral protein of 36 kDa, was originally isolated from Madin-Darby canine kidney cells as a component of detergent-insoluble, glycolipid-enriched complexes containing apical marker [8]
We have previously found that VIP36 has high affinity for high mannose type glycans containing Man-␣-1,2Man residues in Man7–9(GlcNAc)2-Asn peptides [19]
The crystal structure of the exoplasmic/luminal domain of Ca2ϩ-bound VIP36 was solved by the molecular replacement method using the Ca2ϩ-bound ER-Golgi intermediate compartment (ERGIC)-53 carbohydrate recognition domains (CRDs)

Summary

Introduction

VIP36, vesicular-integral protein of 36 kDa, was originally isolated from Madin-Darby canine kidney cells as a component of detergent-insoluble, glycolipid-enriched complexes containing apical marker [8]. This work suggested the Ca2ϩ dependence of carbohydrate binding and the specificity for the D1 arm, Man-␣-1,2-Man-␣1,2-Man residues, of high mannose type glycans (corresponding to Man(D1)-Man(C)-Man[4]; Fig. 1). Study, we showed that VIP36 has a single Ca2ϩ in the CRD structures and that the Ca2ϩ fixes the positions of Asp131, Asn166, and His190 that interact with carbohydrate ligands in the primary binding site

Results

Conclusion