Structure of the amino-terminal domain of Cbl complexed to its binding site on ZAP-70 kinase

Abstract

Cbl is an adaptor protein that functions as a negative regulator of many signalling pathways that start from receptors at the cell surface. The evolutionarily conserved amino-terminal region of Cbl (Cbl-N) binds to phosphorylated tyrosine residues and has cell-transforming activity. Point mutations in Cbl that disrupt its recognition of phosphotyrosine also interfere with its negative regulatory function and, in the case of v-cbl, with its oncogenic potential. In T cells, Cbl-N binds to the tyrosine-phosphorylated inhibitory site of the protein tyrosine kinase ZAP-70. Here we describe the crystal structure of Cbl-N, both alone and in complex with a phosphopeptide that represents its binding site in ZAP-70. The structures show that Cbl-N is composed of three interacting domains: a four-helix bundle (4H), an EF-hand calcium-binding domain, and a divergent SH2 domain that was not recognizable from the amino-acid sequence of the protein. The calcium-bound EF hand wedges between the 4H and SH2 domains and roughly determines their relative orientation. In the ligand-occupied structure, the 4H domain packs against the SH2 domain and completes its phosphotyrosine-recognition pocket. Disruption of this binding to ZAP-70 as a result of structure-based mutations in the 4H, EF-hand and SH2 domains confirms that the three domains together form an integrated phosphoprotein-recognition module.

A missed exit: Reelin sets in motion Dab1 polyubiquitination to put the break on neuronal migration: Figure 1.

“…Indeed, Cbl is abundantly expressed in cortical neurons and contains a phospho-tyrosine recognition domain comprising an EF-hand and a SH2-like structure through which it binds phospho-tyrosine residues, followed by a hydrophobic residue at pY + 4 (fourth residue after the phospho-tyrosine). These are similar to the motifs found at phosphorylation sites Tyr185 and Tyr198 of Dab1 (Lupher et al 1997;Meng et al 1999). Previous studies showed that Cbl can ubiquitinate Dab1, at least in transfected COS7 cells (Suetsugu et al 2004).…”

Tarp regulates earlyChlamydia-induced host cell survival through interactions with the human adaptor protein SHC1

“…By cloning larger portions of STAT1 and STAT2 that included their entire SH2 domain-containing cores (Mao and Chen, 2005), we obtained soluble, monomeric material for these two proteins. In addition, we cloned, expressed, and purified the N-terminal domain of CBL (Meng et al, 1999), which contains a noncanonical SH2 domain. In total, 133 domains representing 103 proteins were used in these studies.…”

The φ29 DNA polymerase:protein-primer structure suggests a model for the initiation to elongation transition

“…This alignment superimposes a four-helix bundle domain from Cbl, a ubiquitin ligase involved in cell signalling, onto the priming domain of terminal protein with a Z-score of 4.7 (PDB code 2CBL; Meng et al, 1999). Since the four-helix bundle is an abundant motif and Cbl is functionally unrelated to terminal protein, this structural similarity appears purely coincidental.…”