Human platelet-derived growth factor (PDGF): purification of PDGF-I and PDGF-II and separation of their reduced subunits.

Human platelet-derived growth factor (PDGF) was purified from lysates of clinically outdated human platelets by a direct procedure that allowed the recovery of active PDGF from stained sodium dodecyl sulfate/polyacrylamide gels. This technique enabled the identification and purification to homogeneity of two active PDGF polypeptides, and with a molecular weight of about 35,000 (PDGF-I) and the other with a molecular weight of about 32,000 (PDGF-II). Reduced PDGF-I produced two inactive subunits, with molecular weights of about 15,000 and 18,000. Reduced PDGF-II also produced two inactive subunits, with molecular weights of about 15,000 and 16,000. It is possible that PDGF-II derives from proteolytic cleavage of PDGF-I.