This family represents the C-terminal domain of BMP and activin membrane-bound inhibitor homolog (BAMBI) which contains the transmembrane domain and a short intracellular domain that, unlike all other known TGF-beta type I or type II receptors, does not encode a serine/threonine-kinase domain. However, it shares sequence homology with the E6 and catalytic loops of receptor serine/threonine kinases [1]. BAMBI is an essential regulator of cell proliferation and differentiation that represses transforming growth factor-beta and enhances Wnt/beta-catenin signalling in various cell types [2]. It stably associates with TGF-beta-family receptors and inhibits BMP and activin as well as TGF-beta signalling [1].

1: Silencing of TGF-beta signalling by the pseudoreceptor BAMBI. Onichtchouk D, Chen YG, Dosch R, Gawantka V, Delius H, Massague J, Niehrs C; Nature 1999;401:480-485. PMID:10519551

2: BAMBI Promotes C2C12 Myogenic Differentiation by Enhancing Wnt/beta-Catenin Signaling. Zhang Q, Shi XE, Song C, Sun S, Yang G, Li X; Int J Mol Sci. 2015;16:17734-17745. PMID:26247931