Crystal structure of a beta-catenin/ axin complex suggests a mechanism for the beta-catenin destruction complex.
The "beta-catenin destruction complex" is central to canonical Wnt/beta-catenin signaling. The scaffolding protein Axin and the tumor suppressor adenomatous polyposis coli protein (APC) are critical components of this complex, required for rapid beta-catenin turnover. We determined the crystal structure of a complex between beta-catenin and the beta-catenin- binding domain of Axin ( Axin- CBD). The Axin- CBD forms a helix that occupies the groove formed by the third and fourth armadillo repeats of beta-catenin and thus precludes the simultaneous binding of other beta-catenin partners in this region. Our biochemical studies demonstrate that, when phosphorylated, the 20-amino acid repeat region of APC competes with Axin for binding to beta-catenin. We propose that a key function of APC in the beta-catenin destruction complex is to remove phosphorylated beta-catenin product from the active site.[1]References
- Crystal structure of a beta-catenin/axin complex suggests a mechanism for the beta-catenin destruction complex. Xing, Y., Clements, W.K., Kimelman, D., Xu, W. Genes Dev. (2003) [Pubmed]
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