Beta-centractin: characterization and distribution of a new member of the centractin family of actin-related proteins
Biochemistry & Molecular Pharmacology
Graduate School of Biomedical Sciences; Department of Biological Chemistry
Medical Subject Headings
Actins; Amino Acid Sequence; Animals; Cytosol; DNA, Complementary; Dogs; Electrophoresis, Gel, Two-Dimensional; Hela Cells; Humans; Microtubule Proteins; *Microtubule-Associated Proteins; Molecular Sequence Data; RNA, Messenger; Tissue Distribution
Life Sciences | Medicine and Health Sciences
An examination of human-expressed sequence tags indicated the existence of an isoform of centractin, an actin-related protein localized to microtubule-associated structures. Using one of these tags, we isolated and determined the nucleotide sequence of a full-length cDNA clone. The protein encoded represents the first example of multiple isoforms of an actin-related protein in a single organism. Northern analysis using centractin-specific probes revealed three species of mRNA in HeLa cells that could encode centractin isoforms. One mRNA encodes the previously-identified centractin (now referred to as alpha-centractin). The full-length cDNA clone isolated using the expressed sequence tag encodes a new member of the centractin family, beta-centractin. A probe specific for alpha-centractin hybridized to the third species of mRNA observed (referred to as gamma-centractin). Comparisons of Northern blots of human tissues indicated that alpha-centractin and beta-centractin mRNAs are equally distributed in all populations of mRNA examined, whereas the expression of gamma-centractin appears to be tissue specific. The amino acid sequence of beta-centractin, deduced from the cDNA, indicates a 91% identity with alpha-centractin, increasing to 96% similarity when conservative amino acid changes are taken into account. As antibodies previously raised against alpha-centractin reacted only poorly with beta-centractin, new antibodies were produced and combined with two-dimensional gel electrophoresis to discriminate the two isoforms. Using this system, the subcellular distribution of the alpha- and beta-isoforms were determined. Both isoforms were found predominantly in the cytosolic fraction as a part of a previously identified 20S complex (referred to as the dynactin complex) with no evidence for a free pool of either isoform. The isoforms were found in a constant ratio of approximately 15:1 (alpha:beta) in the dynactin complex.
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Citation: Mol Biol Cell. 1994 Dec;5(12):1301-10.
Molecular biology of the cell
Clark, Sean W.; Staub, Olivier; Clark, Imran B.; Holzbaur, Erika L. F.; Paschal, Bryce Mark; Vallee, Richard B.; and Meyer, David I., "Beta-centractin: characterization and distribution of a new member of the centractin family of actin-related proteins" (1994). GSBS Student Publications. 235.