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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The parasitic flagellate Giardia is the source of a filamentous protein, giardin, which binds to microtubules. The primary sequence of one giardin chain has been decoded from the base sequences of cDNAs isolated by antibody screens of a library constructed in the expression vector lambda gt11. The amino acid sequence favours a continuous alpha-helical fold for the protein without any inserts of a non-helical character. Analysis of apolar residue positions revealed 35 repeating heptads consistent with coiled-coil structure. This conformation relates giardin to the alpha-type fibrous proteins (k-m-e-f class) like tropomyosin and myosin (also found in Giardia). The giardin sequence has a regular series of skip residues like those at certain positions in the rod section of nematode myosin where the internal apolar seam of the coiled coil is shifted on the helix surface. The skips divide the giardin coil into quasi-equivalent structural segments about 4 nm in length, which might be domains for combining with tubulin subunits in the microtubule surface lattice.
J Mol Biol 1988 Dec 05
PMID:Segmented alpha-helical coiled-coil structure of the protein giardin from the Giardia cytoskeleton. 322 52

We isolated a cDNA clone from the tumorigenic human fibroblast cell line HuT-14 that contains the entire protein coding region of tropomyosin isoform 3 (Tm3) and 781 base pairs of 5'- and 3'-untranslated sequences. Tm3, despite its apparent smaller molecular weight than Tm1 in two-dimensional gels, has the same peptide length as Tm1 (284 amino acids) and shares 83% homology with Tm1. Tm3 cDNA hybridized to an abundant mRNA of 1.3 kilobases in fetal muscle and cardiac muscle, suggesting that Tm3 is related to an alpha fast-tropomyosin. The first 188 amino acids of Tm3 are identical to those of rat or rabbit skeletal muscle alpha-tropomyosin, and the last 71 amino acids differ from those of rat smooth muscle alpha-tropomyosin by only 1 residue. Tm3 therefore appears to be encoded by the same gene that encodes the fast skeletal muscle alpha-tropomyosin and the smooth muscle alpha-tropomyosin via an alternative RNA-splicing mechanism. In contrast to Tm4 and Tm5, Tm3 has a small gene family, with, at best, only one pseudogene.
Mol Cell Biol 1988 Jan
PMID:Cloning and characterization of a cDNA encoding transformation-sensitive tropomyosin isoform 3 from tumorigenic human fibroblasts. 333 57

We have isolated a cDNA clone from a human skeletal muscle library which contains the complete protein-coding sequence of a skeletal muscle alpha-tropomyosin. This cDNA sequence defines a fourth human tropomyosin gene, the hTM alpha gene, which is distinct from the hTMnm gene encoding a closely related isoform of skeletal muscle alpha-tropomyosin. In cultured human fibroblasts, the hTM alpha gene encodes both skeletal-muscle- and smooth-muscle-type alpha-tropomyosins by using an alternative mRNA-splicing mechanism.
Mol Cell Biol 1988 Jan
PMID:Human hTM alpha gene: expression in muscle and nonmuscle tissue. 333 63

HuT-14T is a highly tumorigenic fibroblast cell line which exhibits a reduced steady-state level of beta-actin due to coding mutations in one of two beta-actin alleles. The normal rate of total actin synthesis could be restored in some clones of cells following transfection of the functional beta-actin gene but not following transfection of the functional gamma-actin gene. In gamma-actin gene-transfected substrains that have increased rates of gamma-actin synthesis, beta-actin synthesis is further reduced in a manner consistent with an autoregulatory mechanism, resulting in abnormal ratios of actin isoforms. Thus, both beta- and gamma-actin proteins can apparently regulate the synthesis of their coexpressed isoforms. In addition, decreased synthesis of normal beta-actin seems to correlate with a concomitant down-regulation of tropomyosin isoforms.
Mol Cell Biol 1988 Apr
PMID:Modulation of microfilament protein composition by transfected cytoskeletal actin genes. 338 97

We have isolated clones of human genomic DNA which contain the structural elements of the hTMnm gene. In non-muscle tissue this gene produces a 2.5 kb (1 kb = 10(3) bases or base-pairs) mRNA encoding TM30nm, a 248 amino acid cytoskeletal tropomyosin. In muscle, alternative splicing of this gene results in the expression of a 1.3 kb mRNA encoding a 285 amino acid skeletal muscle alpha-tropomyosin. The hTMnm gene spans at least 42 kb of DNA and consists of 13 exons, only five of which are common to both the 2.5 kb and 1.3 kb transcripts. The boundaries of the exons giving rise to the muscle-specific isoform are identical to the base to those of other genes encoding muscle tropomyosins. A comparison of the structures of exons encoding the amino-terminal sequences of the muscle and non-muscle isoforms suggests that the hTMnm gene has evolved by a specific pattern of exon duplication with alternative splicing.
J Mol Biol 1988 Jun 05
PMID:Organization of the hTMnm gene. Implications for the evolution of muscle and non-muscle tropomyosins. 341 7

The response of permeabilized rabbit fast skeletal muscle fibers to calcium is determined by the troponin T (TnT) and tropomyosin (Tm) isoforms they express. Fibers expressing primarily TnT2f and alpha 2 Tm exhibit steeper pCa/tension relations than those in which either TnT1f or TnT3f and alpha beta Tm predominate. Troponin C extraction studies show that lower slopes do not result from a less concerted transition on the thin filament: the Tn-Tm regulatory strand activates as a unit in all fast fibers. Because the TnT variants differ in their N-terminal segments, and this region overlaps adjacent Tms on the regulatory strand, we propose that both the end-to-end overlap of Tm and the effect of TnT on that interaction are the basis of the concerted transition of the regulatory strand to the active state that occurs in the presence of calcium. Moreover, the effect of different Tn-Tm combinations on the ratio of the affinities of TnC for calcium in the relaxed and active states appears to be a significant determinant of the contractile properties of fast fibers in vivo.
J Mol Biol 1987 Dec 05
PMID:Effect of different troponin T-tropomyosin combinations on thin filament activation. 343 Jun 19

The expression of troponin T in atria and ventricles of adult chicken, rabbit and beef hearts has been studied by two dimensional electrophoresis of soluble extracts from these tissues. The monoclonal antibody, T1/61, has been used to detect the presence of troponin T in the chicken samples. In the chicken only one form of troponin T has been found which is resolved into two spots that probably are due to phosphorylated and non phosphorylated forms. The gels of chicken atria and ventricles are identical with the same patterns, not only of troponin T but also of tropomyosin and myosin light chains. In rabbit and beef the position of troponin T can be located by comparison with the chicken. In the beef it is possible that two forms are present but in the rabbit there appears to be only one. The gels of atria and ventricles of rabbit and beef hearts show differences only in the myosin light chains whereas the expression of tropomyosin is the same. In beef, beta-tropomyosin is found in both tissues. On the evidence of these gels there are no differences in the expression of troponin T or tropomyosin between the atria and ventricles of any of the hearts studied.
J Mol Cell Cardiol 1986 Mar
PMID:Expression of troponin T in atria and ventricles of avian and mammalian hearts. 351 26

We have isolated a cDNA that contains the complete coding sequence of a 3.0 X 10(3) base human fibroblast mRNA together with a large part of its 3' untranslated sequence. The deduced protein sequence is very similar if not identical to the sequence of horse platelet tropomyosin, a 247 amino acid protein. In vitro translation of an SP6 transcript of this cDNA reveals that the protein product of the 3.0 X 10(3) base mRNA is TM30p1, one of the five proteins in human fibroblasts that have been shown to possess the physical and chemical characteristics of tropomyosin. This mRNA is encoded by a gene family that consists of a functional gene and multiple RNA-copy pseudogenes. This family of sequences is distinct from the gene family encoding TM30nm, a cytoskeletal tropomyosin very similar in electrophoretic mobility to TM30p1, but which shows significant differences in primary structure.
J Mol Biol 1987 Mar 05
PMID:Characterization of a cDNA defining a gene family encoding TM30p1, a human fibroblast tropomyosin. 361 96

Mutant human beta-actin genes were introduced into normal human (KD) fibroblasts and the derivative cell line HuT-12, which is immortalized but nontumorigenic, to test their ability to promote conversion to the tumorigenic state. Transfected substrains of HuT-12 fibroblasts that expressed abundant levels of mutant beta-actin (Gly-244----Asp-244) produced subcutaneous tumors in athymic mice after long latent periods (1.5 to 3 months). However, transfected substrains of KD fibroblasts retained their normal finite life span in culture and consequently were incapable of producing tumors. Substrains of HuT-12 cells transfected with the wild-type beta-actin gene and some transfected strains that expressed low or undetectable levels of mutant beta-actin did not produce tumors. Cell lines derived from transfectant cell tumors always exhibited elevated synthesis of the mutant beta-actin, ranging from 145 to 476% of the level expressed by the transfected cells that were inoculated to form the tumor. In general, primary transfectant cells that expressed the highest levels of mutant beta-actin were more tumorigenic than strains that expressed lower levels. The tumor-derived strains were stable in tumorigenicity and produced tumors with shortened latent periods of only 2 to 4 weeks. These findings imply that the primary transfectant strains develop subpopulations of cells that are selected to form tumors because of their elevated rate of exogenous mutant beta-actin synthesis. Actin synthesis and accumulation of gamma-actin mRNA from the endogenous beta- and gamma-actin genes were diminished in tumor-derived strains, apparently to compensate for elevated mutant beta-actin synthesis and maintain the normal cellular concentration of actin. Synthesis of the transformation-sensitive tropomyosin isoforms was decreased along with mutant beta-actin expression. Such modulations in tropomyosin synthesis are characteristically seen in transformation of avian, rodent, and human fibroblasts. Our results suggest that this mutant beta-actin contributes to the neoplastic phenotype of immortalized human fibroblasts by imposing a cytoarchitectural defect and inducing abnormal expression of cytoskeletal tropomyosins.
Mol Cell Biol 1987 Jul
PMID:Expression of transfected mutant beta-actin genes: transitions toward the stable tumorigenic state. 361 99

A new crystalline form of tropomyosin has been produced that diffracts to about 4 A resolution. The crystals are grown at room temperature by slowly lowering the concentration of spermine. This polyamine apparently neutralizes the acidic amino acid side-chains of tropomyosin and allows close side-by-side packing of molecules. The space group is C2, with unit cell dimensions a = 259.7 A, b = 55.3 A, c = 135.6 A, and beta = 97.2 degrees. The tropomyosin molecules appear to be bonded head-to-tail to form straight filaments that run along the crystallographic (332) direction in an arrangement closely related to thin crystalline sheets previously described.
J Mol Biol 1987 May 05
PMID:A new crystal form of tropomyosin. Preliminary X-ray diffraction analysis. 365 11


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