Secondary structure assignment of mouse SOCS3 by NMR defines the domain boundaries and identifies an unstructured insertion in the SH2 domain
- Author(s)
- Babon, JJ; Yao, SG; DeSouza, DP; Harrison, CF; Fabri, LJ; Liepinsh, E; Scrofani, SD; Baca, M; Norton, RS;
- Details
- Publication Year 2005-12,Volume 272,Issue #23,Page 6120-6130
- Journal Title
- FEBS JOURNAL
- Publication Type
- Journal Article
- Abstract
- SOCS3 is a negative regulator of cytokine signalling that inhibits Janus kinase-signal transduction and activator of transcription (JAK-STAT) mediated signal tranduction by binding to phosphorylated tyrosine residues on intracellular subunits of various cytokine receptors, as well as possibly the JAK proteins. SOCS3 consists of a short N-terminal sequence followed by a kinase inhibitory region, an extended SH2 domain and a C-terminal suppressor of cytokine signalling ( SOCS) box. SOCS3 and the related protein, cytokine-inducible SH2-containing protein, are unique among the SOCS family of proteins in containing a region of mostly low complexity sequence, between the SH2 domain and the C-terminal SOCS box. Using NMR, we assigned and determined the secondary structure of a murine SOCS3 construct. The SH2 domain, unusually, consists of 140 residues, including an unstructured insertion of 35 residues. This insertion fits the criteria for a PEST sequence and is not required for phosphotyrosine binding, as shown by isothermal titration calorimetry. Instead, we propose that the PEST sequence has a functional role unrelated to phosphotyrosine binding, possibly mediating efficient proteolytic degradation of the protein. The latter half of the kinase inhibitory region and the entire extended SH2 subdomain form a single alpha-helix. The mapping of the true SH2 domain, and the location of its C terminus more than 50 residues further downstream than predicted by sequence homology, explains a number of previously unexpected results that have shown the importance of residues close to the SOCS box for phosphotyrosine binding.
- Publisher
- BLACKWELL PUBLISHING
- Keywords
- JANUS TYROSINE KINASE; ORNITHINE-DECARBOXYLASE; CRYSTAL-STRUCTURE; ERYTHROPOIETIN RECEPTOR; CYTOKINE SIGNALING-3; PEST HYPOTHESIS; BOX MOTIF; PROTEIN; DEGRADATION; BINDING
- Publisher's Version
- https://doi.org/10.1111/j.1742-4658.2005.05010.x
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- Refer to copyright notice on published article.
Creation Date: 2005-12-01 12:00:00