A natural variant of the cysteine protease virulence factor of group A Streptococcus with an arginine-glycine-aspartic acid (RGD) motif preferentially binds human integrins α(v)β(3) and α(IIb)β(3) - Stockbauer, Kathryn E. (Proc Natl Acad Sci U S A, 1999)