Expression, purification, refolding and crystallization of the carbohydrate-recognition domain of p58/ERGIC-53, an animal C-type lectin involved in export of glycoproteins from the endoplasmic reticulum

p58/ERGIC-53 is a mammalian calcium-dependent lectin that serves as a glycoprotein-sorting receptor between the endoplasmic reticulum (ER) and the Golgi complex. It is a type I transmembrane protein with two lumenal domains, one of which is a carbohydrate-recognition domain (CRD) and homologous to leguminous lectins. The CRD of p58, the rat homologue of human ERGIC-53, was overexpressed in insect cells and Escherichia coli, purified and crystallized using Li₂SO₄ as a precipitant. The crystals belong to space group I222, with unit-cell parameters a = 49.6, b = 86.1, c = 128.1 Å, and contain one molecule per asymmetric unit, corresponding to a packing density of 2.4 Å³ Da^-1. Knowledge of the structure of p58/ERGIC-53 will provide a starting model for understanding receptor-mediated glycoprotein sorting between the ER and the Golgi.