Cell adhesion to low-Mr proteins extractable from mineralized and soft connective tissues.

Guanidinium chloride (4 M) containing proteinase inhibitors was used to extract proteins from porcine calvariae and long bones. The extracted proteins were separated on polyacrylamide slab gels and transferred electrophoretically to nitrocellulose strips. Proteins with cell-adhesion properties were identified by incubating the strips with cells and staining with Amido Black. In addition to binding to fibronectin, both bone cells and fibroblast-like cells adhered to proteins of Mr approximately 30 000 and approximately 14 000-17 000. 4 M-Guanidinium chloride extracts of porcine skin and gingiva yielded cell-binding proteins with similar Mr values. These data suggest that these low-Mr proteins may have a general cell-adhesion function in both soft and mineralized connective tissues.