Tropomyosin isoform 5b is expressed in human erythrocytes: implications of tropomodulin-TM5 or tropomodulin-TM5b complexes in the protofilament and hexagonal organization of membrane skeletons

Sung, L. A., Gao, K. M., Yee, L. J., Temm-Grove, C. J., Helfman, D. M., Lin, J. J. C., Mehrpouryan, M. (2000) Tropomyosin isoform 5b is expressed in human erythrocytes: implications of tropomodulin-TM5 or tropomodulin-TM5b complexes in the protofilament and hexagonal organization of membrane skeletons. Blood, 95 (4). pp. 1473-1480. ISSN 0006-4971

URL: http://www.ncbi.nlm.nih.gov/pubmed/10666227

Abstract

The human erythrocyte membrane skeleton consists of hexagonal lattices with junctional complexes containing F-actin protofilaments of approximately 33-37 nm in length. We hypothesize that complexes formed by tropomodulin, a globular capping protein at the pointed end of actin filaments, and tropomyosin (TM), a rod-like molecule of approximately 33-35 nm, may contribute to the formation of protofilaments, We have previously cloned the human tropomodulin complementary DNA and identified human TM isoform 5 (hTM5), a product of the gamma-TM gene, as one of the major TM isoforms in erythrocytes, We now identify TM5b, a product of the alpha-TM gene, to-be the second major TM isoform, TM5a, the alternatively spliced isoform of the (U-TM gene, which differs by 1 exon and has a weaker actin-binding affinity, however, is not present. TM4, encoded by the delta-TM gene, is not present either. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis, hTM5 comigrated with the slower TM major species in erythrocyte membranes, and hTM5b comigrated with the faster TM major species. TM5b, like TM5, binds strongly to tropomodulin, more so than other TM isoforms, The 2 major TM isoforms, therefore, share several common features: They have 248 residues, are approximately 33-35 nm long, and have high affinities toward F-actin and tropomodulin. These common features may be the key to the mechanism by which protofilaments are formed. Tropomodulin-TM5 or tropomodulin-TM5b complexes may stabilize F-actin in segments of approximately 33-37 nm during erythroid terminal differentiation and may, therefore, function as a molecular ruler. TM5 and TM5b further define the hexagonal geometry of the skeletal network and allow actin-regulatory functions of TMs to be modulated by tropomodulin

Item Type: Paper
Uncontrolled Keywords: ACTIN FILAMENT LENGTH BINDING PROTEIN THIN-FILAMENTS POINTED ENDS FIBROBLAST MUSCLE PURIFICATION CELLS GENE VISUALIZATION
Subjects: bioinformatics > genomics and proteomics > genetics & nucleic acid processing > protein structure, function, modification
bioinformatics > genomics and proteomics > genetics & nucleic acid processing > protein structure, function, modification > protein types > actin
bioinformatics > genomics and proteomics > genetics & nucleic acid processing > protein structure, function, modification > protein types > cytoskeletal proteins
CSHL Authors:
Communities: CSHL labs > Helfman lab
Depositing User: Matt Covey
Date Deposited: 28 Jan 2014 21:53
Last Modified: 28 Jan 2014 21:53
Related URLs:
URI: http://repository.cshl.edu/id/eprint/29455

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