Identification of the domain of alpha-catenin involved in its association with beta-catenin and plakoglobin (gamma-catenin).
alpha-Catenin is a 102-kDa protein exhibiting homology to vincuin, and it forms complexes with cadherins or the tumor-suppressor gene product adenomatous polyposis coli through binding to beta-catenin or plakoglobin (gamma-catenin). The incorporation of alpha-catenin into the cadherin-catenin complexes is a prerequisite for expression of the cell-adhesive activity of cadherins. Using an in vitro assay system involving bacterially expressed proteins, we localized a region in alpha-catenin required for molecular interaction with beta-catenin and plakoglobin. Analysis of various truncated alpha-catenin molecules revealed that amino-terminal residues 48-163 are able to bind to beta-catenin and plakoglobin. Consistent with the observation that beta-catenin and plakoglobin bind to the same region of alpha-catenin, beta-catenin competed with the binding of plakoglobin to alpha-catenin and vice versa. Under the conditions used, beta-catenin bound to alpha-catenin with higher affinity than did plakoglobin. Scatchard analysis indicated that the affinity of the interaction between alpha-catenin and beta-catenin or that between alpha-catenin and plakoglobin was moderately strong (Kd = 3. 8 x 10(-8) and 7.7 x 10(-8), respectively). When transfected into L cells expressing E-cadherin, the amino-terminal region of alpha-catenin (from residue 1 to 226) formed complexes with beta-catenin supporting the in vitro binding experiment results.
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Department of Biochemistry, Faculty of Medicine, Kagoshima University, 8-35-1 Sakuragaoka, Kagoshima 890, Japan.
Ozawa
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D001665:Binding Sites; D001667:Binding, Competitive; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D051180:Desmoplakins; D006801:Humans; D010446:Peptide Fragments / Q000378:metabolism; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015534:Trans-Activators; D051178:alpha Catenin; D051176:beta Catenin; D051185:gamma Catenin
C495273:CTNNA1 protein, human; C495270:CTNNB1 protein, human; D003598:Cytoskeletal Proteins; D051180:Desmoplakins; C495292:JUP protein, human; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D051178:alpha Catenin; D051176:beta Catenin; D051185:gamma Catenin