research communications
The transmembrane intracellular lectin ER–Golgi intermediate compartment protein 53 (ERGIC-53) and the soluble EF-hand multiple coagulation factor deficiency protein 2 (MCFD2) form a complex that functions as a cargo receptor, trafficking various glycoproteins between the endoplasmic reticulum (ER) and the Golgi apparatus. It has been demonstrated that the carbohydrate-recognition domain (CRD) of ERGIC-53 (ERGIC-53CRD) interacts with N-linked glycans on cargo glycoproteins, whereas MCFD2 recognizes polypeptide segments of cargo glycoproteins. Crystal structures of ERGIC-53CRD complexed with MCFD2 and mannosyl oligosaccharides have revealed protein–protein and protein–sugar binding modes. In contrast, the polypeptide-recognition mechanism of MCFD2 remains largely unknown. Here, a 1.60 Å resolution crystal structure of the ERGIC-53CRD–MCFD2 complex is reported, along with three other crystal forms. Comparison of these structures with those previously reported reveal that MCFD2, but not ERGIC-53–CRD, exhibits significant conformational plasticity that may be relevant to its accommodation of various polypeptide ligands.
Keywords: cargo receptor; conformational polymorphism; crystal packing; glycoprotein transport; intracellular lectin; MCFD2; ERGIC-53.
Supporting information
Portable Document Format (PDF) file https://doi.org/10.1107/S2053230X20005452/nw5099sup1.pdf |
PDB references: ERGIC-53–MCFD2, form 1, 4ygb; form 2, 4ygc; form 3, 4ygd; form 4, 4yge