Activins are dimeric growth and differentiation factors which belong to the transforming growth factor-beta (TGF-beta) superfamily of structurally related signaling proteins. Activins signal through a heteromeric complex of receptor serine kinases which include at least two type I (I and IB) and two type II (II and IIB) receptors. These receptors are all transmembrane proteins, composed of a ligand-binding extracellular domain with cysteine-rich region, a transmembrane domain, and a cytoplasmic domain with predicted serine/threonine specificity. Type I receptors are essential for signaling; and type II receptors are required for binding ligands and for expression of type I receptors. Type I and II receptors form a stable complex after ligand binding, resulting in phosphorylation of type I receptors by type II receptors. Type II receptors are considered to be constitutively active kinases. ACVR2B (activin A type IIB receptor) displays a 3- to 4-fold higher affinity for the ligand than activin A type II receptor.
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Protein Aliases: activin A receptor type IIB; activin A receptor, type IIB; Activin receptor type 2B [Precursor]; Activin receptor type IIB; Activin receptor type-2B; ACTR-IIB; ACVR2B
Gene Aliases: ActR-IIB; ACTRIIB; ACVR2B; HTX4