title: Galectin-3 precipitates as a pentamer with synthetic multivalent carbohydrates and forms heterogeneous cross-linked complexes.
abstract: Galectin-3 is unique among the galectin family of animal lectins in its biological activities and structure. Most members of the galectin family including galectin-1 possess apoptotic activities, whereas galectin-3 possesses anti-apoptotic activity. Galectin-3 is also the only chimera type galectin and consists of a nonlectin N-terminal domain and a C-terminal carbohydrate-binding domain. Recent sedimentation equilibrium and velocity studies show that murine galectin-3 is a monomer in the absence and presence of LacNAc, a monovalent sugar. However, quantitative precipitation studies in the present report indicate that galectin-3 precipitates as a pentamer with a series of divalent pentasaccharides with terminal LacNAc residues. Furthermore, the kinetics of precipitation are fast, on the order of seconds. This indicates that although the majority of galectin-3 in solution is a monomer, a rapid equilibrium exists between the monomer and a small percentage of pentamer. The latter, in turn, precipitates with the divalent oligosaccharides, resulting in rapid conversion of monomer to pentamer by mass action equilibria. Mixed quantitative precipitation experiments and electron microscopy suggest that galectin-3 forms heterogenous, disorganized cross-linking complexes with the multivalent carbohydrates. This contrasts with galectin-1 and many plant lectins that form homogeneous, organized cross-linked complexes. The results are discussed in terms of the biological properties of galectin-3.
authors.affiliation: Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
authors.forename: Nisar
authors.initials: N
authors.lastname: Ahmad
authors.forename: Hans-J
authors.initials: HJ
authors.lastname: Gabius
authors.forename: Sabine
authors.initials: S
authors.lastname: André
authors.forename: Herbert
authors.initials: H
authors.lastname: Kaltner
authors.forename: Subramanian
authors.initials: S
authors.lastname: Sabesan
authors.forename: René
authors.initials: R
authors.lastname: Roy
authors.forename: Bingcan
authors.initials: B
authors.lastname: Liu
authors.forename: Frank
authors.initials: F
authors.lastname: Macaluso
authors.forename: C Fred
authors.initials: CF
authors.lastname: Brewer
mesh_terms: D050260:Carbohydrate Metabolism; D011232:Chemical Precipitation; D037502:Galectin 3 / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D008854:Microscopy, Electron; D013329:Structure-Activity Relationship
chemical_list: D037502:Galectin 3