Structural basis for multiple sugar recognition of Jacalin-related human ZG16p lectin [Protein Structure and Folding]

April 30th, 2014 by Kanagawa, M., Liu, Y., Hanashima, S., Ikeda, A., Chai, W., Nakano, Y., Kojima-Aikawa, K., Feizi, T., Yamaguchi, Y.

ZG16p is a soluble mammalian lectin, the first to be described with a Jacalin-related β-prism fold. ZG16p has been reported to bind both to glycosaminoglycans and mannose. In order to determine the structural basis of the multiple sugar-binding properties, we conducted glycan microarray analyses of human ZG16p. We observed that ZG16p preferentially binds to alpha-mannose-terminating short glycans such as Ser/Thr-linked O-mannose, but not to high-mannose type N-glycans. Among sulfated glycosaminoglycan oligomers examined, chondroitin sulfate B and heparin oligosaccharides showed significant binding. Crystallographic studies of human ZG16p lectin in the presence of selected ligands revealed the mechanism of multiple sugar recognition. Manα1-3Man and Glcβ1-3Glc bound in different orientations: the nonreducing end of the former and the reducing end of the latter fitted in the canonical shallow mannose-binding pocket. Solution NMR analysis using 15N-labeled ZG16p defined the heparin-binding region which is on an adjacent flat surface of the protein. On-array competitive binding assays suggest that it is possible for ZG16p to bind simultaneously to both types of ligands. Recognition of a broad spectrum of ligands by ZG16p may account for the multiple functions of this lectin in the formation of zymogen granules via glycosaminoglycan-binding, and in the recognition of pathogens in the digestive system through α-mannose-related recognition.