BINDING-SPECIFICITY OF A BABY HAMSTER-KIDNEY LECTIN FOR H TYPE-I AND TYPE-II CHAINS, POLYLACTOSAMINE GLYCANS, AND APPROPRIATELY GLYCOSYLATED FORMS OF LAMININ AND FIBRONECTIN

The carbohydrate binding specificity of M(r) = 30,000 lectin (CBP30) f rom baby hamster kidney (BHK) cells has been studied by inhibition of binding of the radiolabeled lectin to asialofetuin-Sepharose using mod el oligosaccharides and glycopeptides. CBP30 binds type I or II Gal-be ta(1 --> 3(4))GlcNAc chains but not Gal(beta-1 --> 3)GalNAc. The inhib itory potency of straight chain polylactosamine structures or complex- type branched glycans is increased in proportion to the number of Gal( beta-1 --> 3(4)) units present. Fucosylation or sialylation of termina l galactose residues or further substitution by (alpha-1 --> 3)-linked galactose or N-acetylgalactosamine does not affect binding whereas su bstitution of the penultimate N-acetylglucosamine residue drastically reduces binding. Thus, blood group A, H type I or H type II structures , shows high affinity whereas Le(x), Le(a), and Le(b) structures bind poorly. CBP30 binds to murine Engelbreth-Holm-Swarm (EHS) tumor lamini n and human amniotic fluid fibronection but not human plasma fibronect in. Binding involves polylactosamine glycans as well as tri- and tetra antennary complex-type glycans present in EHS laminin and amniotic flu id fibronectin but absent in plasma fibronectin. Proteolytic fragments of EHS laminin (E1X/Nd, P1, E8, and E3) bind CBP30, but only fragment E8 supports attachment and spreading of BHK cells. BHK cell adhesion to EHS laminin or fragment E8 was not disturbed by CBP30-specific anti bodies, but at relatively high concentrations (45-mu-g/ml) CBP30 inhib ited spreading and partially attachment of cells on laminin.