Endogenous protein phosphorylation in adhesive plaques of substrate-attached fibroblasts

Endogenous protein kinases and acceptor proteins in the focal adhesion plaques of monolayer cells were studied using [γ-³²P]ATP as exogenous substrate. Two major phosphoproteins, p135 and pp105, besides some minor phosphoproteins, were phosphorylated in the substrate-attached material after dislodgement of cells. Evidence was obtained, that suspension cells leave the same components on the wall of the culture vessel, resulting from cell collisions with the wall and not from passive adsorption of secreted components or disintegrated cellular material.