Identification of the Protein 4.1 Binding Interface on Glycophorin C and p55, a Homologue of the Drosophila discs-large Tumor Suppressor Protein

doi:10.1074/jbc.270.2.715

Identification of the Protein 4.1 Binding Interface on Glycophorin C and p55, a Homologue of the Drosophila discs-large Tumor Suppressor Protein (*)

From the (1)Department of Biomedical Research, St. Elizabeth's Medical Center, Tufts University School of Medicine, Boston, Massachusetts 02135 and
(2)Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138

^§ To whom correspondence should be addressed:
Dept. of Biomedical Research, ACH4, St. Elizabeth's Medical Center, 736 Cambridge St., Boston, MA 02135.
Tel. 617-789-3118; Fax: 617-789-3111.

Abstract

Protein 4.1 is the prototype of a family of proteins that include ezrin, talin, brain tumor suppressor merlin, and tyrosine phosphatases. All members of the protein 4.1 superfamily share a highly conserved N-terminal 30-kDa domain whose biological function is poorly understood. It is believed that the attachment of the cytoskeleton to the membrane may be mediated via this 30-kDa domain, a function that requires formation of multiprotein complexes at the plasma membrane. In this investigation, synthetically tagged peptides and bacterially expressed proteins were used to map the protein 4.1 binding site on human erythroid glycophorin C, a transmembrane glycoprotein, and on human erythroid p55, a palmitoylated peripheral membrane phosphoprotein. The results show that the 30-kDa domain of protein 4.1 binds to a 12-amino acid segment within the cytoplasmic domain of glycophorin C and to a positively charged, 39-amino acid motif in p55. Sequences similar to this charged motif are conserved in other members of the p55 superfamily, including the Drosophila discs-large tumor suppressor protein. Our data provide new insights into how protein 4.1, glycophorin C, p55, and their non-erythroid homologues, interact with the cytoskeleton to exert their physiological effects.

Footnotes

↵* This work was supported by the National Institutes of Health Grants HL51445, HL37462 (to A. H. C.), and HL17411 (to D. B.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

MAGUKs

membrane-associated guanylate kinase homologues

GST

glutathione S-transferase

SH3

src homology 3

Dlg

Drosophila discs-large tumor suppressor protein

Hdlg

human homologue of the discs-large tumor suppressor protein

ELISA

enzyme-linked immunosorbent assay.
- Received August 17, 1994.
- Revision received October 28, 1994.