Activin receptor type-2B( Activin receptor type IIB; ACTR-IIB ) On ligand binding, forms a receptor complex consisting of two type II and two type I transmembrane serine/threonine kinases. Type II receptors phosphorylate and activate type I receptors which autophosphorylate, then bind and activate SMAD transcriptional regulators. Receptor for activin A, activin B and inhibin A. [Subcellular Location] Membrane; Single-pass type I membrane protein. Belongs to the protein kinase superfamily. T