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Biochem J. 2010 Oct 1;431(1):93-102. doi: 10.1042/BJ20100314.

Identification and biophysical assessment of the molecular recognition mechanisms between the human haemopoietic cell kinase Src homology domain 3 and ALG-2-interacting protein X.

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State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, 155 Yang Qiao Xi Lu, Fuzhou, Fujian 350002, China.


SFKs (Src family kinases) are central regulators of many signalling pathways. Their functions are tightly regulated through SH (Src homology) domain-mediated protein-protein interactions. A yeast two-hybrid screen using SH3 domains as bait identified Alix [ALG-2 (apoptosis-linked gene 2)-interacting protein X] as a novel Hck (haemopoietic cell kinase) SH3 domain interactor. The Alix-Hck-SH3 interaction was confirmed in vitro by a GST (glutathione transferase) pull-down assay and in intact cells by a mammalian two-hybrid assay. Furthermore, the interaction was demonstrated to be biologically relevant in cells. Through biophysical experiments, we then identified the PRR (proline-rich region) motif of Alix that binds Hck-SH3 and determined a dissociation constant of 34.5 μM. Heteronuclear NMR spectroscopy experiments were used to map the Hck-SH3 residues that interact with an ALIX construct containing the V and PRR domains or with the minimum identified interacting motif. Finally, SAXS (small-angle X-ray scattering) analysis showed that the N-terminal PRR of Alix is unfolded, at least before Hck-SH3 recognition. These results indicate that residues outside the canonical PxxP motif of Alix enhance its affinity and selectivity towards Hck-SH3. The structural framework of the Hck-Alix interaction will help to clarify how Hck and Alix assist during virus budding and cell-surface receptor regulation.

[Indexed for MEDLINE]

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