title: L-29, an endogenous lectin, binds to glycoconjugate ligands with positive cooperativity.
abstract: The soluble mammalian lactose-binding lectins L-14-I and L-29 are both secreted and bind to oligosaccharides on laminin, a large extracellular matrix glycoprotein containing polylactosamine chains. Because of the potential functional significance of these lectin-laminin interactions, we compared quantitative aspects of L-14-I and L-29 binding to immobilized laminin using recombinant lectins labeled with 125I. We report that the concentration-dependent binding of L-29 exhibits positive cooperativity whereas binding of L-14-I does not. Cooperative binding of L-29 can also occur on glycoconjugate substrates other than laminin and is not dependent on cystine bond formation or aggregation in solution. L-29 contains repetitive sequences within the N-terminal domain not present in L-14-I. This domain is not required for binding activity, but is required for positive cooperativity. Though the precise mechanism of interaction of L-29 with laminin remains to be determined, it apparently results in assembly of a lectin aggregate on the substrate surface, which could have important functional consequences.
authors.affiliation: Department of Psychiatry, University of California, San Francisco 94143.
authors.forename: S M
authors.initials: SM
authors.lastname: Massa
authors.forename: D N
authors.initials: DN
authors.lastname: Cooper
authors.forename: H
authors.initials: H
authors.lastname: Leffler
authors.forename: S H
authors.initials: SH
authors.lastname: Barondes
mesh_terms: D000818:Animals; D000943:Antigens, Differentiation / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D017364:Collagenases / Q000378:metabolism; D004229:Dithiothreitol / Q000494:pharmacology; D004926:Escherichia coli / Q000235:genetics; D037502:Galectin 3; D006001:Glycoconjugates / Q000378:metabolism*; D007457:Iodine Radioisotopes; D007785:Lactose / Q000378:metabolism; D007797:Laminin / Q000378:metabolism*; D008623:Mercaptoethanol / Q000494:pharmacology; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid
chemical_list: D000943:Antigens, Differentiation; D037502:Galectin 3; D006001:Glycoconjugates; D007457:Iodine Radioisotopes; D007797:Laminin; D010446:Peptide Fragments; D011994:Recombinant Proteins; D008623:Mercaptoethanol; D017364:Collagenases; D007785:Lactose; D004229:Dithiothreitol