Biochemical and immunochemical comparison of fibronectin and polynectin from porcine plasma

Polynectin, a glycoprotein of porcine blood plasma (also known as glycine-rich gelatin-binding protein (Isemura, M., Sato, N., and Yosizawa, Z. (1982) J. Biol. Chem. 257, 14854-14857] is similar to fibronectin with respect to binding characteristics to affinity gels. However, no immunoprecipitation reaction was observed either between polynectin and anti-fibronectin antiserum, or between fibronectin and anti-polynectin antiserum prepared in the present experiments. No cross-reaction was found between fibronectin and polynectin by enzyme-linked immunosorbent assays. Immunohistochemical studies revealed the presence in abundance of polynectin in intestinal and gastric glands. It was found that the pattern of distribution of polynectin was entirely different from that of fibronectin. Polynectin, in contrast to fibronectin, exhibited no cell attachment-promoting effects on BHK-21, a baby hamster kidney cell line, and a cell line of human embryonic lung fibroblasts. In addition, changes in binding characteristics to affinity gels after reduction and alkylation differed between polynectin and fibronectin. Although both proteins appear to have similar carbohydrate chains in view of the similar reactivities with lectins, the results of the present experiments demonstrated that polynectin is entirely different from fibronectin.