A sialic acid-binding lectin from ovine placenta: purification, specificity and interaction with actin.

A sialic-acid-specific lectin from ovine placental cotyledons was purified by affinity chromatography on bovine submaxillary mucin-agarose followed by gel filtration, and it showed a molecular weight of 65000 by sodium dodecylsulfate-polyacrylamide gel electrophoresis. This lectin has the capacity to interact with actin, since it binds to actin-F in a cosedimentation assay and it acts as a mediator in the binding of actin to the affinity column. The lectin agglutinated rabbit and rat erythrocytes, but not human A, B or O erythrocytes. Haemagglutination inhibition assays of different saccharides, glycoproteins and glycolipids indicate that this lectin has affinity for sialic acid, which is enhanced by its O-acetylation. The N-terminal sequence of the protein shows 92% identity with rabbit and porcine uterine calreticulin.