Cell adhesion and spreading factor. Chemical modification studies

The purified fetal calf serum factor that promotes cell adhesion and spreading of baby hamster kidney cells on tissue culture substrata has been subjected to a variety of chemical modifications and then tested for activity. These studies have shown that modification of the carbohydrate portions of the factor by glycosidic enzymes or by periodate oxidation did not alter its ability to promote cell spreading. On the other hand, modification of some protein portions of the factor by proteolytic enzymes or by specific modification of -COOH groups, tyrosine residues, or tryptophan residues resulted in a marked inhibition of factor activity. Modification of protein -SH groups, -NH₂ groups, or methionine residues did not affect factor activity. Control experiments indicate that the various modifications were directed at the activity of the factor and not its adsorption onto the substrata.