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Publication Abstract from PubMed

Xenopus laevis (African clawed frog) has two types of proto-type galectins that are similar to mammalian galectin-1 in amino acid sequence. One type, comprising xgalectin-Ia and -Ib, is regarded as being equivalent to galectin-1, and the other type, comprising xgalectin-Va and -Vb, is expected to be a unique galectin subgroup. The latter is considerably abundant in frog skin, however, its biological function remains unclear. We determined the crystal structures of two proto-type galectins, xgalectin-Ib and -Va. The structures showed that both galectins formed a mammalian galectin-1-like homodimer, and furthermore, xgalectin-Va formed a homotetramer. This tetramer structure has not been reported for other galectins. Gel filtration and other experiments indicated that xgalectin-Va was in a dimer-tetramer equilibrium in solution, and lactose binding enhanced the tetramer formation. The residues involved in the dimer-dimer association were conserved in xgalectin-Va and -Vb, and one of the Xenopus (Silurana) tropicalis proto-type galectins, but not in xgalectin-Ia and -Ib, and other galectin-1-equivalent proteins. Xgalectin-Va preferred Galbeta1-3GalNAc and not Galbeta1-4GlcNAc, while xgalectin-Ib preferred Galbeta1-4GlcNAc as well as human galectin-1. Xgalectin-Va/Vb would have diverged from the galectin-1 group with accompanying acquisition of the higher oligomer formation and altered ligand selectivity.

Crystal structure of a Xenopus laevis skin proto-type galectin, close to but distinct from galectin-1.,Nonaka Y, Ogawa T, Yoshida H, Shoji H, Nishi N, Kamitori S, Nakamura T Glycobiology. 2015 Mar 24. pii: cwv020. PMID:25804418^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.