A protein complex consisting of two chains of platelet-derived growth factor (PDGF) subunits. PDGF dimers bind to PDGF receptors in the plasma membrane and induce receptor dimerization and activation. PDGFs are involved in a wide variety of signaling processes. PDGFs are found in all vertebrates where at least 2 different chains (A and B) exist. In human (and other mammals), four types of PDGF chains (A, B, C, and D) are known which form five different dimers (AA, AB, BB, CC and DD).
PDGF-BB dimer