Di-glucose binding within endoplasmic reticulum. Malectin is a membrane-anchored protein of the endoplasmic reticulum that recognises and binds Glc2-N-glycan. It carries a signal peptide from residues 1-26, a C-terminal transmembrane helix from residues 255-274, and a highly conserved central part of approximately 190 residues followed by an acidic, glutamate-rich region. Carbohydrate-binding is mediated by the four aromatic residues, Y67, Y89, Y116, and F117 and the aspartate at D186. NMR-based ligand-screening studies has shown binding of the protein to maltose and related oligosaccharides, on the basis of which the protein has been designated "malectin", and its endogenous ligand is found to be Glc2-high-mannose N-glycan.