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Cofractionation experiments showed that ?-catenin that interacts with cadherin is in a heterodimer with -catenin, but Wnt signaling induces a monomeric form of ?-catenin that interacts with a transcription factor complex. After enriching for cadherins, ?-catenin can be detected using antibodies to either NH2-terminal or COOH-terminal regions; but in the cadherin-free fraction only the NH2-terminal antibody binds. The team hypothesizes that the ?-catenin protein is folded back on itself in its monomeric form and, as such, is available for transcription complex binding but not for adhesion duties.
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Gottardi speculates that a post-translational modification is responsible for the conformational change but does not yet know what that modification is. Furthermore, she thinks this sort of molecular segregation may be a common mechanism cells use to allow one protein to do multiple jobs, without the more common function soaking up all the protein required for a temporally regulated one.(The cytoplasmic protein ?-catenin is ess) |
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