Acts as a fibronectin-dependent adhesin and invasin. Binds host (in this case human) fibronectin, plasmin, plasminogen, and human serum albumin. Where the bacteria adhere to human cells there is major recruitment of microvilli which seem to fuse to cover the streptococcal chains. Antibodies to this protein reduce bacterial growth in human blood. Cells lacking this gene adhere to and invade human cell lines half as well as wild-type bacteria. They grow less well in human blood, perhaps because they are more resistant to phagocytosis. Has potential use as a vaccine component.