Smad proteins exist as monomers in vivo and undergo homo- and hetero-oligomerization upon activation by serine/threonine kinase receptors

Kawabata M, Inoue H, Hanyu A, Imamura T, Miyazono K.
EMBO J. 1998 Jul 15;17(14):4056-65.
PMID: 9670020 PMCID: PMC1170738 DOI: 10.1093/emboj/17.14.4056