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Structural flexibility regulates phosphopeptide-binding activity of the tyrosine kinase binding domain of Cbl-c.

Takeshita K., Tezuka T., Isozaki Y., Yamashita E., Suzuki M., Kim M., Yamanashi Y., Yamamoto T., Nakagawa A.

Through their ubiquitin ligase activity, Cbl-family proteins suppress signalling mediated by protein-tyrosine kinases (PTKs), but can also function as adaptor proteins to positively regulate signalling. The tyrosine kinase binding (TKB) domain of this family is critical for binding with tyrosine-phosphorylated target proteins. Here, we analysed the crystal structure of the TKB domain of Cbl-c/Cbl-3 (Cbl-c TKB), which is a distinct member of the mammalian Cbl-family. In comparison with Cbl TKB, Cbl-c TKB showed restricted structural flexibility upon phosphopeptide binding. A mutation in Cbl-c TKB augmenting this flexibility enhanced its binding to target phosphoproteins. These results suggest that proteins, post-translational modifications or mutations that alter structural flexibility of the TKB domain of Cbl-family proteins could regulate their binding to target phosphoproteins and thereby, affect PTK-mediated signalling.

J. Biochem. 152:487-495(2012) [PubMed] [Europe PMC]