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- Title
The L3 loop and C-terminal phosphorylation jointly define Smad protein trimerization.
- Authors
Chacko, Benoy M.; Qin, Bin; Correia, John J.; Lam, Suvana S.; de Caestecker, Mark P.; Lin, Kai
- Abstract
Smad proteins mediate the transforming growth factor β responses. C-terminal phosphorylation of R-Smads leads to the recruitment of Smad4 and the formation of active signaling complexes. We investigated the mechanism of phosphorylation-induced Smad complex formation with an activating pseudo-phosphorylated Smad3. Pseudo-phosphorylated Smad3 has a greater propensity to homotrimerize, and recruits Smad4 to form a heterotrimer containing two Smad3 and one Smad4. The trimeric interaction is mediated through conserved interfaces to which tumorigenic mutations map. Furthermore, a conserved Arg residue within the L3 loop, located near the C-terminal phosphorylation sites of the neighboring subunit, is essential for trimerization. We propose that the phosphorylated C-terminal residues interact with the L3 loop of the neighboring subunit to stabilize the trimer interaction.
- Subjects
PHOSPHORYLATION; PROTEINS
- Publication
Nature Structural Biology, 2001, Vol 8, Issue 3, p248
- ISSN
1072-8368
- Publication type
Article
- DOI
10.1038/84995