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Lopez Davila AJ, Zhu L, Fritz L, Kraft T, Chalovich JM. The Positively Charged C-Terminal Region of Human Skeletal Troponin T Retards Activation and Decreases Calcium Sensitivity. Biochemistry 2020; 59:4189-4201. [PMID: 33074652 DOI: 10.1021/acs.biochem.0c00499] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Calcium binding to troponin C (TnC) activates striated muscle contraction by removing TnI (troponin I) from its inhibitory site on actin. Troponin T (TnT) links TnI with tropomyosin, causing tropomyosin to move from an inhibitory position on actin to an activating position. Positive charges within the C-terminal region of human cardiac TnT limit Ca2+ activation. We now show that the positively charged region of TnT has an even larger impact on skeletal muscle regulation. We prepared one variant of human skeletal TnT that had the C-terminal 16 residues truncated (Δ16) and another with an added C-terminal Cys residue and Ala substituted for the last 6 basic residues (251C-HAHA). Both mutants reduced (based on S1 binding kinetics) or eliminated (based on acrylodan-tropomyosin fluorescence) the first inactive state of actin at <10 nM free Ca2+. 251C-HAHA-TnT and Δ16-TnT mutants greatly increased ATPase activation at 0.2 mM Ca2+, even without high-affinity cross-bridge binding. They also shifted the force-pCa curve of muscle fibers to lower Ca2+ by 0.8-1.2 pCa units (the larger shift for 251C-HAHA-TnT). Shifts in force-pCa were maintained in the presence of para-aminoblebbistatin. The effects of modification of the C-terminal region of TnT on the kinetics of S1 binding to actin were somewhat different from those observed earlier with the cardiac analogue. In general, the C-terminal region of human skeletal TnT is critical to regulation, just as it is in the cardiac system, and is a potential target for modulating activity.
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Affiliation(s)
- Alfredo Jesus Lopez Davila
- Institute of Molecular and Cell Physiology, Hannover Medical School, Carl-Neuberg-Street 1, 103-Block 1-Ebene 03-1010, Hannover 30625, Germany
| | - Li Zhu
- Department of Biochemistry & Molecular Biology, Brody School of Medicine at East Carolina University, Greenville, North Carolina 27834, United States
| | - Leon Fritz
- Institute of Molecular and Cell Physiology, Hannover Medical School, Carl-Neuberg-Street 1, 103-Block 1-Ebene 03-1010, Hannover 30625, Germany
| | - Theresia Kraft
- Institute of Molecular and Cell Physiology, Hannover Medical School, Carl-Neuberg-Street 1, 103-Block 1-Ebene 03-1010, Hannover 30625, Germany
| | - Joseph M Chalovich
- Department of Biochemistry & Molecular Biology, Brody School of Medicine at East Carolina University, Greenville, North Carolina 27834, United States
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Johnson D, Angus CW, Chalovich JM. Stepwise C-Terminal Truncation of Cardiac Troponin T Alters Function at Low and Saturating Ca 2. Biophys J 2018; 115:702-712. [PMID: 30057009 DOI: 10.1016/j.bpj.2018.06.028] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Revised: 06/19/2018] [Accepted: 06/29/2018] [Indexed: 11/16/2022] Open
Abstract
Activation of striated muscle contraction occurs in response to Ca2+ binding to troponin C. The resulting reorganization of troponin repositions tropomyosin on actin and permits activation of myosin-catalyzed ATP hydrolysis. It now appears that the C-terminal 14 amino acids of cardiac troponin T (TnT) control the level of activity at both low and high Ca2+. We made a series of C-terminal truncation mutants of human cardiac troponin T, isoform 2, to determine if the same residues of TnT are involved in the low and high Ca2+ effects. We measured the effect of these mutations on the normalized ATPase activity at saturating Ca2+. Changes in acrylodan tropomyosin fluorescence and the degree of Ca2+ stimulation of the rate of binding of rigor myosin subfragment 1 to pyrene-labeled actin-tropomyosin-troponin were measured at low Ca2+. These measurements define the distribution of actin-tropomyosin-troponin among the three regulatory states. Residues SKTR and GRWK of TnT were required for the functioning of TnT at both low and high Ca2+. Thus, the effects on forming the inactive B-state and in retarding formation of the active M-state require the same regions of TnT. We also observed that the rate of binding of rigor subfragment 1 to pyrene-labeled regulated actin at saturating Ca2+ was higher for the truncation mutants than for wild-type TnT. This violated an assumption necessary for determining the B-state population by this kinetic method.
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Affiliation(s)
- Dylan Johnson
- Department of Biochemistry, Brody School of Medicine, East Carolina University, Greenville, North Carolina
| | - C William Angus
- Department of Biochemistry, Brody School of Medicine, East Carolina University, Greenville, North Carolina
| | - Joseph M Chalovich
- Department of Biochemistry, Brody School of Medicine, East Carolina University, Greenville, North Carolina.
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Katrukha IA. Human cardiac troponin complex. Structure and functions. BIOCHEMISTRY (MOSCOW) 2014; 78:1447-65. [DOI: 10.1134/s0006297913130063] [Citation(s) in RCA: 104] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Kobayashi M, Debold EP, Turner MA, Kobayashi T. Cardiac muscle activation blunted by a mutation to the regulatory component, troponin T. J Biol Chem 2013; 288:26335-26349. [PMID: 23897817 DOI: 10.1074/jbc.m113.494096] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The striated muscle thin filament comprises actin, tropomyosin, and troponin. The Tn complex consists of three subunits, troponin C (TnC), troponin I (TnI), and troponin T (TnT). TnT may serve as a bridge between the Ca(2+) sensor (TnC) and the actin filament. In the short helix preceding the IT-arm region, H1(T2), there are known dilated cardiomyopathy-linked mutations (among them R205L). Thus we hypothesized that there is an element in this short helix that plays an important role in regulating the muscle contraction, especially in Ca(2+) activation. We mutated Arg-205 and several other amino acid residues within and near the H1(T2) helix. Utilizing an alanine replacement method to compare the effects of the mutations, the biochemical and mechanical impact on the actomyosin interaction was assessed by solution ATPase activity assay, an in vitro motility assay, and Ca(2+) binding measurements. Ca(2+) activation was markedly impaired by a point mutation of the highly conserved basic residue R205A, residing in the short helix H1(T2) of cTnT, whereas the mutations to nearby residues exhibited little effect on function. Interestingly, rigor activation was unchanged between the wild type and R205A TnT. In addition to the reduction in Ca(2+) sensitivity observed in Ca(2+) binding to the thin filament, myosin S1-ADP binding to the thin filament was significantly affected by the same mutation, which was also supported by a series of S1 concentration-dependent ATPase assays. These suggest that the R205A mutation alters function through reduction in the nature of cooperative binding of S1.
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Affiliation(s)
- Minae Kobayashi
- From the Department of Physiology and Biophysics, Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, Illinois 60612 and.
| | - Edward P Debold
- the Department of Kinesiology, University of Massachusetts, Amherst, Massachusetts 01003
| | - Matthew A Turner
- the Department of Kinesiology, University of Massachusetts, Amherst, Massachusetts 01003
| | - Tomoyoshi Kobayashi
- From the Department of Physiology and Biophysics, Center for Cardiovascular Research, University of Illinois at Chicago, Chicago, Illinois 60612 and
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Jin JP, Chong SM. Localization of the two tropomyosin-binding sites of troponin T. Arch Biochem Biophys 2010; 500:144-50. [PMID: 20529660 DOI: 10.1016/j.abb.2010.06.001] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2010] [Revised: 06/01/2010] [Accepted: 06/02/2010] [Indexed: 11/28/2022]
Abstract
Troponin T (TnT) binds to tropomyosin (Tm) to anchor the troponin complex in the thin filament, and it thus serves as a vital link in the Ca(2+) regulation of striated muscle contraction. Pioneer work three decades ago determined that the T1 and T2 chymotryptic fragments of TnT each contains a Tm-binding site. A more precise localization of the two Tm-binding sites of TnT remains to be determined. In the present study, we tested serial deletion constructs of TnT and carried out monoclonal antibody competition experiments to show that the T1 region Tm-binding site involves mainly a 39 amino acids segment in the N-terminal portion of the conserved middle region of TnT. We further employed another set of TnT fragments to locate the T2 region Tm-binding site to a segment of 25 amino acids near the beginning of the T2 fragment. The localization of the two Tm-binding sites of TnT provided new information for the structure-function relationship of TnT and the anchoring of troponin complex on muscle thin filament.
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Affiliation(s)
- J-P Jin
- Department of Physiology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
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Cao S, Ho GH, Lin VCL. Tetratricopeptide repeat domain 9A is an interacting protein for tropomyosin Tm5NM-1. BMC Cancer 2008; 8:231. [PMID: 18699990 PMCID: PMC2538545 DOI: 10.1186/1471-2407-8-231] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2008] [Accepted: 08/12/2008] [Indexed: 02/07/2023] Open
Abstract
Background Tetratricopeptide repeat domain 9A (TTC9A) protein is a recently identified protein which contains three tetratricopeptide repeats (TPRs) on its C-terminus. In our previous studies, we have shown that TTC9A was a hormonally-regulated gene in breast cancer cells. In this study, we found that TTC9A was over-expressed in breast cancer tissues compared with the adjacent controls (P < 0.00001), suggesting it might be involved in the breast cancer development process. The aim of the current study was to further elucidate the function of TTC9A. Methods Breast samples from 25 patients including the malignant breast tissues and the adjacent normal tissues were processed for Southern blot analysis. Yeast-two-hybrid assay, GST pull-down assay and co-immunoprecipitation were used to identify and verify the interaction between TTC9A and other proteins. Results Tropomyosin Tm5NM-1 was identified as one of the TTC9A partner proteins. The interaction between TTC9A and Tm5NM-1 was further confirmed by GST pull-down assay and co-immunoprecipitation in mammalian cells. TTC9A domains required for the interaction were also characterized in this study. The results suggested that the first TPR domain and the linker fragment between the first two TPR domains of TTC9A were important for the interaction with Tm5NM-1 and the second and the third TPR might play an inhibitory role. Conclusion Since the primary function of tropomyosin is to stabilize actin filament, its interaction with TTC9A may play a role in cell shape and motility. In our previous results, we have found that progesterone-induced TTC9A expression was associated with increased cell motility and cell spreading. We speculate that TTC9A acts as a chaperone protein to facilitate the function of tropomyosins in stabilizing microfilament and it may play a role in cancer cell invasion and metastasis.
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Affiliation(s)
- Shenglan Cao
- School of Biological Sciences, Nanyang Technological University, Singapore.
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Brown JH, Cohen C. Regulation of muscle contraction by tropomyosin and troponin: how structure illuminates function. ADVANCES IN PROTEIN CHEMISTRY 2005; 71:121-59. [PMID: 16230111 DOI: 10.1016/s0065-3233(04)71004-9] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Jerry H Brown
- Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, Massachusetts 02454, USA
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Hammell RL, Hitchcock-DeGregori SE. The sequence of the alternatively spliced sixth exon of alpha-tropomyosin is critical for cooperative actin binding but not for interaction with troponin. J Biol Chem 1997; 272:22409-16. [PMID: 9278391 DOI: 10.1074/jbc.272.36.22409] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Tropomyosins, a family of highly conserved coiled-coil actin binding proteins, can differ as a consequence of alternative expression of several exons (Lees-Miller, J., and Helfman, D. (1991) BioEssays 13, 429-437). Exon 6, which encodes residues 189-213 in long, 284-residue tropomyosins, has two alternative forms, exon 6a or 6b, both highly conserved throughout evolution. In alpha-tropomyosin, exon 6a or 6b is not specific to any one of the nine isoforms. Exon 6b encodes part of a putative Ca2+-sensitive troponin binding site in striated muscle tropomyosins, suggesting that the exon 6-encoded region may be specialized for certain tropomyosin functions. A series of recombinant, unacetylated tropomyosin exon 6 deletion and substitution mutants and chimeras was expressed in Escherichia coli to determine the requirements of exon 6 for tropomyosin function. Functional properties of the tropomyosins were defined by actin affinity measured by cosedimentation, troponin T affinity using a newly developed biosensor assay, and regulation of the actomyosin MgATPase. The region of tropomyosin encoded by exon 6 affects actin affinity but not thin filament assembly, troponin T binding, or regulation with troponin. The tropomyosins with exon 6a or 6b function normally whether a striated muscle exon 9a or smooth/non-muscle exon 9d is present. However, the effect of deleting 21 amino acids encoded by exon 6 or replacing it with a GCN4 leucine zipper sequence depends on the COOH-terminal sequence.
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Affiliation(s)
- R L Hammell
- Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA
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Palmiter KA, Solaro RJ. Molecular mechanisms regulating the myofilament response to Ca2+: implications of mutations causal for familial hypertrophic cardiomyopathy. Basic Res Cardiol 1997; 92 Suppl 1:63-74. [PMID: 9202846 DOI: 10.1007/bf00794070] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In this chapter we consider a current perception of the molecular mechanisms controlling myofilament activation with emphasis on alterations that may occur in familial hypertrophic cardiomyopathy (FHC). FHC is a sarcomeric disease (100) with an autosomal dominant pattern of heritability (27, 51). There is a substantial body of evidence implicating missense mutations in the beta-MHC gene as causal for the development of this disease. Recently, mutations in genes of two thin filament regulatory proteins, cardiac troponin T(cTnT) and alpha-tropomyosin (alpha-Tm), have also been linked to FHC. The commonality among the functional consequences of these mutations remains an important question. This review discusses how these pathological mutations may impact the activation process by disrupting critical structure function relations in both the thick and thin filaments.
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Affiliation(s)
- K A Palmiter
- Department of Physiology and Biophysics, University of Illinois at Chicago 60612, USA
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Hammell RL, Hitchcock-DeGregori SE. Mapping the functional domains within the carboxyl terminus of alpha-tropomyosin encoded by the alternatively spliced ninth exon. J Biol Chem 1996; 271:4236-42. [PMID: 8626768 DOI: 10.1074/jbc.271.8.4236] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Tropomyosins are highly conserved, coiled-coil actin binding proteins found in most eukaryotic cells. Striated and smooth muscle alpha-tropomyosins differ by the regions encoded by exons 2 and 9. Unacetylated smooth tropomyosin expressed in Escherichia coli binds actin with high affinity, whereas unacetylated striated tropomyosin requires troponin, found only in striated muscle, for strong actin binding. The residues encoded by exon 9 cause these differences (Cho, Y.-J., and Hitchcock-DeGregori, S. E. (1991) Proc. Natl. Acad. Sci. U. S. A. 88, 10153-10157). We mapped the functional domains encoded by the alpha-tropomyosin exon 9a (striated muscle-specific) and 9d (constitutively expressed), by measuring actin binding and regulation of the actomyosin MgATPase by tropomyosin exon 9 chimeras and truncation mutants expressed in E. coli. We have shown that: 1) the carboxyl-terminal nine residues define the actin affinity of unacetylated tropomyosin; 2) in the presence of Ca2+, the entire exon 9a is required for troponin to promote fully high affinity actin binding; 3) the first 18 residues encoded by exon 9a are critical for the interaction of troponin with tropomyosin on the thin filament, even in the absence of Ca2+. The results give new insight into the structural requirements of tropomyosin for thin filament assembly and regulatory function.
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Affiliation(s)
- R L Hammell
- Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA
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Fisher D, Wang G, Tobacman LS. NH2-terminal truncation of skeletal muscle troponin T does not alter the Ca2+ sensitivity of thin filament assembly. J Biol Chem 1995; 270:25455-60. [PMID: 7592713 DOI: 10.1074/jbc.270.43.25455] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
To investigate how Ca2+ binding to troponin C regulates muscle contraction, the Ca(2+)-sensitive properties of thin filament assembly were studied as the tropomyosin binding, NH2-terminal region of troponin T was progressively shortened. Troponin complexes were prepared that contained skeletal muscle troponin C, troponin I, and either intact troponin T (TnT) (residues 1-259) or fragment TnT-(70-259), TnT-(151-259), or TnT-(159-259). In the absence of Ca2+ their respective affinities for pyrene-labeled tropomyosin were 2.3 x 10(7) M-1, 1.2 x 10(7) M-1, 1.9 x 10(5) M-1, and 1.9 x 10(5) M-1. Ca2+ had only a small effect on these affinities: 1.1 x 10(7) M-1 for whole troponin, 2 x 10(5) M-1 for troponin-(151-259), and 2.8 x 10(5) M-1 for troponin-(159-259). Forms of troponin that bound weakly to tropomyosin in the absence of actin increased the actin affinity of tropomyosin only 2-3-fold, even in the absence of Ca2+; weak binding of troponin to tropomyosin correlated with weak effects on tropomyosin-actin binding. In contrast, whole troponin had an approximately 500-fold effect on tropomyosin binding to actin, regardless of whether Ca2+ was present. The small effect of Ca2+ on the energetics of thin filament assembly is not attributable to the amino-terminal region of troponin T. The results suggest that Ca2+ causes the interaction between actin and the globular region of troponin to switch between two energetically similar states.
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Affiliation(s)
- D Fisher
- Department of Biochemistry, University of Iowa, Iowa City 52242, USA
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Fleenor DE, Hickman KH, Lindquester GJ, Devlin RB. Avian cardiac tropomyosin gene produces tissue-specific isoforms through alternative RNA splicing. J Muscle Res Cell Motil 1992; 13:55-63. [PMID: 1556172 DOI: 10.1007/bf01738428] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We have isolated a quail cardiac tropomyosin gene which encodes three distinct isoforms through the use of alternative exon splicing. Characterization of cDNA clones produced by this gene indicate that the gene encodes a unique 284 amino acid cardiac tropomyosin isoform, along with a 248 amino acid cytoskeletal and 284 amino acid smooth muscle isoforms. Northern analyses indicate that the gene is primarily expressed in cardiac muscle, with only minor expression of the cytoskeletal and smooth muscle transcripts.
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Affiliation(s)
- D E Fleenor
- Biology Department, Emory University, Atlanta, GA 30322
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14
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Frenkel MJ, Savin KW, Bakker RE, Ward CW. Characterization of cDNA clones coding for muscle tropomyosin of the nematode Trichostrongylus colubriformis. Mol Biochem Parasitol 1989; 37:191-9. [PMID: 2514356 DOI: 10.1016/0166-6851(89)90151-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The host-protective antigen from detergent-solubilised extracts of the sheep intestinal helminth Trichostrongylus colubriformis has been identified as tropomyosin. Complementary DNA clones coding for T. colubriformis muscle tropomyosin have been isolated and characterised as the first step in obtaining recombinant protein to carry out more extensive vaccination trials. The clones represent an mRNA of 1544 bases, including a relatively long 5' untranslated sequence of 307 bases and a 3' non-coding region of 344 bases. The mRNA codes for a highly alpha-helical protein of 284 residues with a molecular weight of 33,000; characteristics typically observed for the muscle tropomyosins of higher organisms. The T. colubriformis protein has 58% sequence identity with rabbit and Drosophila melanogaster muscle tropomyosins, and the differences in the protein sequence are randomly distributed throughout the molecule. There is complete identity between the three sequences for the N-terminal 9 residues, the region believed to be essential for the polymerisation of tropomyosin molecules and for binding to actin and troponin.
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Affiliation(s)
- M J Frenkel
- CSIRO Division of Biotechnology, Parkville, Victoria, Australia
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15
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Jin JP, Lin JJ. Isolation and Characterization of cDNA Clones Encoding Embryonic and Adult Isoforms of Rat Cardiac Troponin T. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)71702-x] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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16
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Bucher EA, de la Brousse FC, Emerson CP. Developmental and Muscle-specific Regulation of Avian Fast Skeletal Troponin T Isoform Expression by mRNA Splicing. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)63884-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Heeley DH, Smillie LB. Interaction of rabbit skeletal muscle troponin T and F-actin at physiological ionic strength. Biochemistry 1988; 27:8227-32. [PMID: 3233205 DOI: 10.1021/bi00421a036] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Troponin T has been shown to interact significantly with F-actin at 150 mM KC1 by using an F-actin pelleting assay and 125I-labeled proteins. While troponin T fragment T1 (residues 1-158) fails to pellet with F-actin, fragment T2 (residues 159-259) mimics the binding properties of the intact molecule. The weak competition of T2 binding to F-actin, shown by subfragments of T2, indicates that the interaction site(s) encompass(es) an extensive segment of troponin T. The extent of pelleting of troponin T (or T2) with F-actin is only marginally altered in the binary complex troponin IT (or T2), indicating that the direct interactions either of troponin T (or T2) or of troponin I, or both, with F-actin are weakened when these components are incorporated into a binary complex. The binding of troponin T (or T2) is moderately (-Ca2+) or more extensively reduced (+Ca2+) in the presence of troponin C. The pelleting of Tn-T seen in the presence of Tn-C (-Ca2+) and Tn-I was further reduced when either Tn-I or Tn-C (-Ca2+) was added, respectively, to form a fully reconstituted Tn complex. As noted by others, whole troponin shows little sensitivity to Ca2+ in its binding to F-actin (-tropomyosin). These and other observations, taken together with the restoration of troponin IC (+/- Ca2+) binding to F-actin by troponin T, implicate a role for the interaction of troponin T and F-actin in the thin filament assembly.
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Affiliation(s)
- D H Heeley
- Department of Biochemistry, University of Alberta, Edmonton, Canada
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Hitchcock-DeGregori SE, Lewis SF, Mistrik M. Lysine reactivities of tropomyosin complexed with troponin. Arch Biochem Biophys 1988; 264:410-6. [PMID: 3135780 DOI: 10.1016/0003-9861(88)90306-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The relative reactivities of lysine residues of tropomyosin complexed with troponin have been measured in order to locate the binding site of troponin on tropomyosin in a complex between the two native proteins. The lysines were labeled with acetic anhydride using a competitive labeling procedure and the relative reactivities of tropomyosin lysine containing peptides were compared to those from tropomyosin labeled in the absence of troponin (S. E. Hitchcock-DeGregori, S. F. Lewis, and T. M.-T. Chou, (1985) Biochemistry 24, 3305-3314). Analysis of about two-thirds of the lysines indicates that troponin affects the reactivities of lysines along the length of the tropomyosin, indicating long-range effects. The inferred binding site is more extensive than previously reported, about 25 nm, extending from res. 136 to the carboxy-terminus and to res. 30 beyond the end-to-end overlap in the amino-terminal region of the next tropomyosin molecule.
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Affiliation(s)
- S E Hitchcock-DeGregori
- Department of Anatomy, UMDNJ-Robert Wood Johnson Medical School, Piscataway, New Jersey 08854
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Clayton L, Reinach FC, Chumbley GM, MacLeod AR. Organization of the hTMnm gene. Implications for the evolution of muscle and non-muscle tropomyosins. J Mol Biol 1988; 201:507-15. [PMID: 3418707 DOI: 10.1016/0022-2836(88)90633-x] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
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.
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Affiliation(s)
- L Clayton
- Ludwig Institute for Cancer Research, MRC Centre, Cambridge, U.K
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21
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Heald RW, Hitchcock-DeGregori SE. The structure of the amino terminus of tropomyosin is critical for binding to actin in the absence and presence of troponin. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)60708-2] [Citation(s) in RCA: 101] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Tobacman LS. Structure-function studies of the amino-terminal region of bovine cardiac troponin T. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)69119-7] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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23
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A novel hybrid alpha-tropomyosin in fibroblasts is produced by alternative splicing of transcripts from the skeletal muscle alpha-tropomyosin gene. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)47688-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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24
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Heeley D, Golosinska K, Smillie L. The effects of troponin T fragments T1 and T2 on the binding of nonpolymerizable tropomyosin to F-actin in the presence and absence of troponin I and troponin C. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)61061-0] [Citation(s) in RCA: 105] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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25
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Mak AS, Roseborough G, Baker H. Tropomyosin from human erythrocyte membrane polymerizes poorly but binds F-actin effectively in the presence and absence of spectrin. BIOCHIMICA ET BIOPHYSICA ACTA 1987; 912:157-66. [PMID: 3828355 DOI: 10.1016/0167-4838(87)90084-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Actin in the human erythrocyte forms short protofilaments which are only long enough to accommodate tropomyosin monomers (Shen, B.W., Josephs, R. and Steck, T.L. (1986) J. Cell Biol. 102, 997-1006). This interaction between actin and tropomyosin monomers is predicted to be weak, since tropomyosin polymerization parallels its affinity for F-actin. We examine the binding of human erythrocyte tropomyosin to actin in the presence and absence of spectrin and its ability to polymerize. The binding of human erythrocyte tropomyosin to F-actin is not affected appreciably by the present of spectrin. Saturating F-actin with erythrocyte tropomyosin, however, weakens the binding of spectrin dimers to actin. Although tropomyosin from human erythrocyte and rabbit cardiac muscle have similar affinity for F-actin, the polymerizability of erythrocyte tropomyosin as determined by viscosity measurements is much reduced relative to muscle tropomyosin. This unusual property of erythrocyte tropomyosin is likely due to differences in its primary structure from other known tropomyosin at the amino and carboxyl terminal regions which are responsible for its head-to-tail polymerization and cooperative binding to F-actin. Analysis of the distribution of tyrosine by 2-dimensional tryptic mapping of 125I-labelled erythrocyte tropomyosin shows that tyrosine at positions 162, 214, 221, 261 and 267 in rabbit cardiac tropomyosin are conserved in human erythrocyte tropomyosin but Tyr-60 is absent. This observation suggests that erythrocyte tropomyosin has a carboxyl terminal region similar to its muscle counterparts but its amino terminal region resembles that of platelet tropomyosin which also lacks Tyr-60.
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26
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MacLeod AR, Talbot K, Smillie LB, Houlker C. Characterization of a cDNA defining a gene family encoding TM30p1, a human fibroblast tropomyosin. J Mol Biol 1987; 194:1-10. [PMID: 3612796 DOI: 10.1016/0022-2836(87)90710-8] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
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.
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27
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Kay CM, McCubbin WD, Sykes BD. Biophysical studies on the calcium trigger of muscle contraction. Biopolymers 1987; 26 Suppl:S123-44. [PMID: 3580494 DOI: 10.1002/bip.360260013] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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28
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29
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Van Eyk JE, Cachia PJ, Ingraham RH, Hodges RS. Studies on the regulatory complex of rabbit skeletal muscle: Contributions of troponin subunits and tropomyosin in the presence and absence of Mg2+ to the acto-S1 ATPase activity. ACTA ACUST UNITED AC 1986. [DOI: 10.1007/bf01025962] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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30
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Ohtsuki I, Maruyama K, Ebashi S. Regulatory and cytoskeletal proteins of vertebrate skeletal muscle. ADVANCES IN PROTEIN CHEMISTRY 1986; 38:1-67. [PMID: 3541537 DOI: 10.1016/s0065-3233(08)60525-2] [Citation(s) in RCA: 163] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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31
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Basi GS, Storti RV. Structure and DNA sequence of the tropomyosin I gene from Drosophila melanogaster. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(17)36169-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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32
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Yamawaki-Kataoka Y, Helfman DM. Rat embryonic fibroblast tropomyosin 1. cDNA and complete primary amino acid sequence. J Biol Chem 1985. [DOI: 10.1016/s0021-9258(17)38588-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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33
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Sanders C, Smillie LB. Amino acid sequence of chicken gizzard beta-tropomyosin. Comparison of the chicken gizzard, rabbit skeletal, and equine platelet tropomyosins. J Biol Chem 1985. [DOI: 10.1016/s0021-9258(17)39602-3] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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34
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Ruiz-Opazo N, Weinberger J, Nadal-Ginard B. Comparison of alpha-tropomyosin sequences from smooth and striated muscle. Nature 1985; 315:67-70. [PMID: 3838802 DOI: 10.1038/315067a0] [Citation(s) in RCA: 97] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Tropomyosins are a closely related family of proteins with a dimeric alpha-coiled-coil structure. Skeletal isoforms are composed of two types of subunits, alpha and beta which, in turn, are assorted into two main molecular species alpha alpha and alpha beta. Both isoforms are present in different molar ratios in individual skeletal muscle types. In small mammals, however, only alpha-chain is expressed in cardiac muscle. Tropomyosin, in association with the troponin complex (troponin-I, -T and -C) plays a central role in the Ca2+-dependent regulation of vertebrate striated muscle contraction. On the other hand, despite structural similarities with the striated isoforms, the function of this protein in smooth muscle and non-muscle cells remains unknown, because in these cells contraction is thought to be regulated by myosin-linked processes independently of tropomyosin. Here we report the nucleotide sequences of cloned complementary DNAs for rat striated and smooth muscle alpha-tropomyosin. Comparison of the derived amino-acid sequences reveals the existence of tissue-specific peptides that delimit the putative troponin-I and troponin-T binding domains of tropomyosin. S1-nuclease mapping studies reveal the existence of three distinct alpha-tropomyosin messenger RNA isoforms each encoding a different protein; these isoforms are tissue-specific, developmentally regulated and most probably encoded by the same gene.
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35
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Chong P, Gillam S. Purification of biologically active rubella virus antigens by immunoaffinity chromatography. J Virol Methods 1985; 10:261-8. [PMID: 3988877 DOI: 10.1016/0166-0934(85)90066-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A general procedure for isolating biologically active rubella virus antigens (VPI, Mr = 61,000; VP2, Mr = 45,000; VP3, Mr = 36,000) by monoclonal antibody affinity chromatography is described. Complexes formed between monoclonal antibodies and rubella virus antigens were found to be stable either at low pH or in Tris buffer containing detergent and high salt, but were efficiently dissociated by 5% diethanolamine, pH 11.5, or 50 mM lithium diiodosalicylate buffer, pH 8.0. Chromatographically purified rubella viral antigens retained their antigenicity as determined by enzyme-linked immunosorbent assays. Biological studies showed that rubella structural proteins VP2 and VP3 had no hemagglutinin function while the mixture of VP1 and VP2 and VP3 directly demonstrated hemagglutination activity. These results indicate that VP1 is at least in part responsible for the hemagglutinin function of rubella virus.
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36
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Helfman DM, Feramisco JR, Ricci WM, Hughes SH. Isolation and sequence of a cDNA clone that contains the entire coding region for chicken smooth-muscle alpha-tropomyosin. J Biol Chem 1984. [DOI: 10.1016/s0021-9258(18)89867-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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37
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Han KK, Richard C, Delacourte A. Chemical cross-links of proteins by using bifunctional reagents. ACTA ACUST UNITED AC 1984. [DOI: 10.1016/0020-711x(84)90064-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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38
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Leavis PC, Gergely J. Thin filament proteins and thin filament-linked regulation of vertebrate muscle contraction. CRC CRITICAL REVIEWS IN BIOCHEMISTRY 1984; 16:235-305. [PMID: 6383715 DOI: 10.3109/10409238409108717] [Citation(s) in RCA: 346] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Recent developments in the field of myofibrillar proteins will be reviewed. Consideration will be given to the proteins that participate in the contractile process itself as well as to those involved in Ca-dependent regulation of striated (skeletal and cardiac) and smooth muscle. The relation of protein structure to function will be emphasized and the relation of various physiologically and histochemically defined fiber types to the proteins found in them will be discussed.
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Mak AS, Golosinska K, Smillie LB. Induction of nonpolymerizable tropomyosin binding to F-actin by troponin and its components. J Biol Chem 1983. [DOI: 10.1016/s0021-9258(17)43864-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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40
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Abstract
The non-muscle tropomyosins (TMs), isolated from such tissues as platelets, brain and thyroid, are structurally very similar to the muscle TMs, being composed of two highly alpha-helical subunits wound around each other to form a rod-like molecule. The non-muscle TMs are shorter than the muscle TMs; sequence analysis demonstrates that each subunit of equine platelet TM consists of 247 amino acids, 37 fewer than for skeletal muscle TM. The major differences in sequence between platelet and skeletal muscle TM are found near the amino and carboxyl terminal ends of the proteins. Probably as the result of such alterations, the non-muscle TMs aggregate in a linear end-to-end manner much more weakly than do the muscle TMs. Since end-to-end interactions are responsible for the highly cooperative manner in which TM binds to actin, the non-muscle TMs have a lower affinity for actin filaments than do the muscle TMs. However, the attachment of other proteins to actin (e.g. the Tn-I subunit of skeletal muscle troponin or the S-1 subfragment of skeletal muscle myosin) can increase the affinity of actin filaments for non-muscle TM. The non-muscle TMs interact functionally with the Tn-I component of skeletal muscle troponin to inhibit the ATPase activity of muscle actomyosin and with whole troponin to regulate the muscle actomyosin ATPase in a Ca++-dependent manner, even though one of the binding sites for troponin on skeletal TM is missing in non-muscle TM. A novel actomyosin regulatory system can be produced using Tn-I, calmodulin and non-muscle TM; in this case inhibition is released when the non-muscle TM detaches from the actin filament in the presence of Ca++. Although it has not yet been demonstrated that the non-muscle TMs participate in a Ca++-dependent contractile regulatory system in vivo it does appear that they are associated with actin filaments in vivo.
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41
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Pearlstone JR, Smillie LB. Effects of troponin-I plus-C on the binding of troponin-T and its fragments to alpha-tropomyosin. Ca2+ sensitivity and cooperativity. J Biol Chem 1983. [DOI: 10.1016/s0021-9258(18)32959-4] [Citation(s) in RCA: 84] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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