I-SMADs reside in the nucleus presumably to be sequestered from the BMP2:receptor complex and thus avoid inappropriate silencing of the signalling pathway. Upon activation of the signalling pathway, I-SMADs exit the nucleus and are recruited to the signalling BMP2:receptor complex. I-SMADs directly bind to the so-called L45 loop of the type I receptor, the site of binding of R-SMADs. Thus, I-SMADs competitively inhibit the activation/phosphorylation of R-SMADs.
Tajima, Y, Goto, K, Yoshida, M, Shinomiya, K, Sekimoto, T, Yoneda, Y, Miyazono, K, Imamura, T
Murakami, G, Watabe, T, Takaoka, K, Miyazono, K, Imamura, T
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