Identification of the Domain of α-Catenin Involved in Its Association with β-Catenin and Plakoglobin (γ-Catenin)

doi:10.1074/jbc.272.17.11017

Identification of the Domain of α-Catenin Involved in Its Association with β-Catenin and Plakoglobin (γ-Catenin)*

Hiroya Obama and
Masayuki Ozawa^‡

From the Department of Biochemistry, Faculty of Medicine, Kagoshima University, 8-35-1 Sakuragaoka, Kagoshima 890, Japan

^‡To whom correspondence should be addressed. Tel.: 81-99-275-5246; Fax: 81-99-264-5618.

Abstract

α-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 β-catenin or plakoglobin (γ-catenin). The incorporation of α-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 α-catenin required for molecular interaction with β-catenin and plakoglobin. Analysis of various truncated α-catenin molecules revealed that amino-terminal residues 48–163 are able to bind to β-catenin and plakoglobin. Consistent with the observation that β-catenin and plakoglobin bind to the same region of α-catenin, β-catenin competed with the binding of plakoglobin to α-catenin and vice versa. Under the conditions used, β-catenin bound to α-catenin with higher affinity than did plakoglobin. Scatchard analysis indicated that the affinity of the interaction between α-catenin and β-catenin or that between α-catenin and plakoglobin was moderately strong (K_d = 3.8 × 10⁻⁸ and 7.7 × 10⁻⁸, respectively). When transfected into L cells expressing E-cadherin, the amino-terminal region of α-catenin (from residue 1 to 226) formed complexes with β-catenin supporting the in vitro binding experiment results.

Footnotes

↵* This work was supported by Grant 07273258 from the Ministry of Education, Science, and Culture of Japan and a grant from the Ciba-Geigy Foundation (Japan) for the Promotion of Science. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

MBP

maltose-binding protein

GST

glutathione S-transferase

HA

hemagglutinin

PAGE

polyacrylamide gel electrophoresis.
- Received May 21, 1996.
- Revision received December 9, 1996.