activin complex
A nonsteroidal regulator, composed of two covalently linked inhibin beta subunits, inhibin beta-A and inhibin beta-B (sometimes known as activin beta or activin/inhibin beta). There are three forms of activin complex, activin A, which is composed of 2 inhibin beta-A subunits, activin B, which is composed of 2 inhibin beta-B subunits, and activin AB, which is composed of an inhibin beta-A and an inhibin beta-B subunit.
platelet-derived growth factor complex
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).