Isoform Cloning, Actin Binding, and Chromosomal Localization of Human Erythroid Dematin, a Member of the Villin Superfamily (*)
- From the (1) Department of Biomedical Research, St. Elizabeth's Medical Center, Tufts University School of Medicine, Boston, Massachusetts 02135, the Division of Genetics, Children's Hospital, Harvard Medical School, and the
- (2) Department of Pathology, Beth Israel Hospital, Harvard Medical School, Boston, Massachusetts 02115
- § To whom correspondence and reprint requests should be addressed: ACH4, Biomedical Research, St. Elizabeth's Medical Center, 736 Cambridge St., Boston, MA 02135. Tel.: 617-789-3118; Fax: 617-789-3111.
Abstract
Dematin is an actin-bundling protein of the erythroid membrane skeleton and is abundantly expressed in human brain, heart, skeletal muscle, kidney, and lung. The 48-kDa subunit of dematin contains a headpiece domain which was originally identified in villin, an actin-binding protein of the brush-border cytoskeleton. The headpiece domain of villin is essential for its morphogenic function in vivo. Here we report the primary structure of 52-kDa subunit of dematin which differs from the 48-kDa subunit by a 22-amino-acid insertion within its headpiece domain. A unique feature of the insertion sequence of the 52-kDa subunit is its homology to erythrocyte protein 4.2. The insertion sequence also includes a cysteine residue which may explain the formation of sulfhydryl-linked trimers of dematin. Actin binding measurements using recombinant fusion proteins revealed that each monomer of dematin contains two F-actin binding sites: one in the headpiece domain and the other in the undefined N-terminal domain. Although the actin bundling activity of intact dematin was abolished by phosphorylation, no effect of phosphorylation was observed on the actin binding activity of fusion proteins. Using somatic cell hybrid panels and fluorescence in situ hybridization, the dematin gene was localized on the short arm of chromosome 8. The dematin locus, 8p21.1, is distal to the known locus of human erythroid ankyrin (8p11.2) and may contribute to the etiology of hemolytic anemia in a subset of patients with severe hereditary spherocytosis.
Footnotes
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↵* This work was supported by National Institutes of Health Grants HL51445 and HL37462 (to A. H. C.) and HD18568 and the Beth Israel Pathology Foundation, Inc. (to J. H. M. K.). 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.
The nucleotide sequence(s) reported in this paper has been submitted to the GenBank®/EMBL Data Bank with accession number(s) U28389[GenBank® Link].
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↵1 The abbreviations used are:
- PCR
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polymerase chain reaction
- GST
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glutathione S-transferase
- DAPI
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4,6-diamidino-2-phenylindole
- PEST
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proline-glutamic acid-serine-threonine-rich regions.
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↵2A. C. Azim, J. H. M. Knoll, A. H. Beggs, and A. H. Chishti, unpublished data.
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- Received November 3, 1994.
- Revision received February 8, 1995.
