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Kang CH, Jung WY, Kang YH, Kim JY, Kim DG, Jeong JC, Baek DW, Jin JB, Lee JY, Kim MO, Chung WS, Mengiste T, Koiwa H, Kwak SS, Bahk JD, Lee SY, Nam JS, Yun DJ, Cho MJ. AtBAG6, a novel calmodulin-binding protein, induces programmed cell death in yeast and plants. Cell Death Differ 2006; 13:84-95. [PMID: 16003391 DOI: 10.1038/sj.cdd.4401712] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Calmodulin (CaM) influences many cellular processes by interacting with various proteins. Here, we isolated AtBAG6, an Arabidopsis CaM-binding protein that contains a central BCL-2-associated athanogene (BAG) domain. In yeast and plants, overexpression of AtBAG6 induced cell death phenotypes consistent with programmed cell death (PCD). Recombinant AtBAG6 had higher affinity for CaM in the absence of free Ca2 + than in its presence. An IQ motif (IQXXXRGXXXR, where X denotes any amino-acid) was required for Ca2 +-independent CaM complex formation and single amino-acid changes within this motif abrogated both AtBAG6-activated CaM-binding and cell death in yeast and plants. A 134-amino-acid stretch, encompassing both the IQ motif and BAG domain, was sufficient to induce cell death. Agents generating oxygen radicals, which are known to be involved in plant PCD, specifically induced the AtBAG6 transcript. Collectively, these results suggest that AtBAG6 is a stress-upregulated CaM-binding protein involved in plant PCD.
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Affiliation(s)
- C H Kang
- Division of Applied Life Science (BK21 program) and Environmental Biotechnology National Core Research Center, Graduate School of Gyeongsang National University, Jinju 660-701, Korea
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2
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Abstract
The IQ motif is widely distributed in both myosins and non-myosins and is quite common in the database that includes more than 900 Pfam entries. An examination of IQ motif-containing proteins that are known to bind calmodulin (CaM) indicates a wide diversity of biological functions that parallel the Ca2+-dependent targets. These proteins include a variety of neuronal growth proteins, myosins, voltage-operated channels, phosphatases, Ras exchange proteins, sperm surface proteins, a Ras Gap-like protein, spindle-associated proteins and several proteins in plants. The IQ motif occurs in some proteins with Ca2+-dependent CaM interaction where it may promote Ca2+-independent retention of CaM. The action of the IQ motif may result in complex signaling as observed for myosins and the L-type Ca2+ channels and is highly localized as required for sites of neuronal polarized growth and plasticity, fertilization, mitosis and cytoskeletal organization. The IQ motif associated with the unconventional myosins also promotes Ca2+ regulation of the vectorial movement of cellular constituents to these sites. Additional regulatory roles for this versatile motif seem likely.
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Affiliation(s)
- Martin Bähler
- Institut für Allegemeine Zoologie und Genetik, Westfälische Wilhelms Universität, Münster, Germany
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3
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Welikson RE, Buck SH, Patel JR, Moss RL, Vikstrom KL, Factor SM, Miyata S, Weinberger HD, Leinwand LA. Cardiac myosin heavy chains lacking the light chain binding domain cause hypertrophic cardiomyopathy in mice. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:H2148-58. [PMID: 10362699 DOI: 10.1152/ajpheart.1999.276.6.h2148] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Myosin is a chemomechanical motor that converts chemical energy into the mechanical work of muscle contraction. More than 40 missense mutations in the cardiac myosin heavy chain (MHC) gene and several mutations in the two myosin light chains cause a dominantly inherited heart disease called familial hypertrophic cardiomyopathy. Very little is known about the biochemical defects in these alleles and how the mutations lead to disease. Because removal of the light chain binding domain in the lever arm of MHC should alter myosin's force transmission but not its catalytic function, we tested the hypothesis that such a mutant MHC would act as a dominant mutation in cardiac muscle. Hearts from transgenic mice expressing this mutant myosin are asymmetrically hypertrophied, with increases in mass primarily restricted to the cardiac anterior wall. Histological examination demonstrates marked cellular hypertrophy, myocyte disorganization, small vessel coronary disease, and severe valvular pathology that included thickening and plaque formation. Skinned myocytes and multicellular preparations from transgenic hearts exhibited decreased Ca2+ sensitivity of tension and decreased relaxation rates after flash photolysis of diazo 2. These experiments demonstrate that alterations in myosin force transmission are sufficient to trigger the development of hypertrophic cardiomyopathy.
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Affiliation(s)
- R E Welikson
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado 80309, USA
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4
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Roopnarine O, Leinwand LA. Functional analysis of myosin mutations that cause familial hypertrophic cardiomyopathy. Biophys J 1998; 75:3023-30. [PMID: 9826622 PMCID: PMC1299973 DOI: 10.1016/s0006-3495(98)77743-4] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
We have studied the actin-activated ATPase activities of three mutations in the motor domain of the myosin heavy chain that cause familial hypertrophic cardiomyopathy. We placed these mutations in rodent alpha-cardiac myosin to establish the relevance of using rodent systems for studying the biochemical mechanisms of the human disease. We also wished to determine whether the biochemical defects in these mutant alleles correlate with the severity of the clinical phenotype of patients with these alleles. We expressed histidine-tagged rat cardiac myosin motor domains along with rat ventricular light chain 1 in mammalian COS cells. Those myosins studied were wild-type alpha-cardiac and three mutations in the alpha-cardiac myosin heavy chain head (Arg249Gln, Arg403Gln, and Val606Met). These mutations in human beta-cardiac myosin heavy chain have predominantly moderate, severe, and mild clinical phenotypes, respectively. The crystal structure of the skeletal myosin head shows that the Arg249Gln mutation is near the ATP-binding site and the Arg403Gln and Val606Met mutations are in the actin-binding region. Expressed histidine-tagged alpha-motor domains retain physiological ATPase properties similar to those derived from cardiac tissue. All three myosin mutants show defects in the ATPase activity, with the degree of enzymatic impairment of the mutant myosins correlated with the clinical phenotype of patients with the disease caused by the corresponding mutation.
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Affiliation(s)
- O Roopnarine
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309 USA
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5
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Weissbach L, Bernards A, Herion DW. Binding of myosin essential light chain to the cytoskeleton-associated protein IQGAP1. Biochem Biophys Res Commun 1998; 251:269-76. [PMID: 9790945 DOI: 10.1006/bbrc.1998.9371] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The 190 kD human IQGAP1 protein, by virtue of its N-terminal calponin-homology domain, is found associated with the actin cytoskeleton, and is capable of cross-linking actin filaments. IQGAP1 complexes with several proteins, including the Rho family GTPases Cdc42 and Rac, as well as calmodulin. It was previously noted that one of the IQ motifs of IQGAP1 displays significant similarity to a myosin heavy chain IQ motif responsible for binding the calmodulin-related myosin essential light chain (ELC). Employing the yeast two-hybrid methodology as well as in vitro binding experiments, we present evidence that a truncated version of IQGAP1 can interact with the myosin ELC. This interaction may have significant consequences for various cellular processes that involve actomyosin contractility, and suggests that the biological targets of the ELC may not be restricted to the myosin heavy chain.
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Affiliation(s)
- L Weissbach
- Orthopaedic Research Laboratories, Massachusetts General Hospital, Boston, Massachusetts, 02114, USA.
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6
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Weissbach L, Settleman J, Kalady M, Snijders A, Murthy A, Yan Y, Bernards A. Identification of a human rasGAP-related protein containing calmodulin-binding motifs. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)32023-9] [Citation(s) in RCA: 179] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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7
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Eldin P, Le Cunff M, Vosberg HP, Mornet D, Léger JJ. Mapping of the actomyosin interfaces. Proc Natl Acad Sci U S A 1994; 91:2772-6. [PMID: 8146189 PMCID: PMC43452 DOI: 10.1073/pnas.91.7.2772] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Recombinant DNA methods were used to obtain soluble, undenatured fragments of the heavy chain of myosin subfragment 1 (S-1). These fragments were of preselected lengths and could include protease-sensitive segments that are destroyed when other preparation methods are used. Actin binding by each of the three contiguous segments (residues 1-248, 249-524, and 518-722, essentially spanning the entire S-1 heavy chain) was demonstrated. ATP binding, comparable to that of native S-1, was obtained only with a segment consisting of residues 1-524. Competition among the various fragments for actin was also studied. The data are discussed in relation to the recently reported resolved structure of S-1 [Rayment, I., Rypnieski, R. W., Schmidt-Bäse, K., Smith, R., Tomchick, D. R., Benning, M. M., Winkelmann, D. A., Wesenberg, G. & Holden, H. M. (1993) Science 261, 50-58].
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Affiliation(s)
- P Eldin
- Institut National de la Santé et de la Recherche Médicale, Faculté de Pharmacie Bât. K, Montpellier, France
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8
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Epp TA, Dixon IM, Wang HY, Sole MJ, Liew CC. Structural organization of the human cardiac alpha-myosin heavy chain gene (MYH6). Genomics 1993; 18:505-9. [PMID: 8307559 DOI: 10.1016/s0888-7543(11)80006-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The human myocardium expresses two cardiac myosin heavy chain (MyHC) isoforms, alpha and beta, that exist in tandem array on chromosome 14q12. We have previously sequenced the entire human cardiac beta-MyHC gene and now report the complete nucleotide sequence of the human cardiac alpha-MyHC, encompassing 26,159 bp as well as the entire 4484-bp 5'-flanking intergenic region. The gene (MYH6) consists of 39 exons, 37 of which contain coding information. The 5'-untranslated region is split into 3 exons, with the third exon containing the AUG translation initiation codon. With the exception of the 13th intron of the human cardiac beta-MyHC, which is not present within the alpha-isogene, all exon/intron boundaries are conserved. Conspicuous sequence motifs contained within the alpha-MyHC gene include four Alu repeats, a single (GT)n element, and a homopurine-homopyrimidine tract containing 23 GAA repeating units followed by 10 GAG repeating units. Comparison of the encoded amino acid sequence with a previously reported human alpha-MyHC cDNA sequence reveals several potential polymorphisms.
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Affiliation(s)
- T A Epp
- Department of Clinical Biochemistry, Toronto Hospital, University of Toronto, Ontario, Canada
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9
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Liao L, Sindhwani R, Leinwand L, Diamond B, Factor S. Cardiac alpha-myosin heavy chains differ in their induction of myocarditis. Identification of pathogenic epitopes. J Clin Invest 1993; 92:2877-82. [PMID: 7504694 PMCID: PMC288490 DOI: 10.1172/jci116909] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
BALB/c mice develop autoimmune myocarditis after immunization with mouse cardiac myosin, whereas C57B/6 mice do not. To define the immunogenicity and pathogenicity of cardiac myosin in BALB/c mice, we immunized mice with different forms of cardiac myosin. These studies demonstrate the discordance of immunogenicity and pathogenicity of myosin heavy chains. The cardiac alpha-myosin heavy chains of BALB/c and C57B/6 mice differ by two residues that are near the junction of the head and rod in the S2 fragment of myosin. Myosin preparations from both strains are immunogenic in susceptible BALB/c as well as in nonsusceptible C57B/6 mice; however, BALB/c myosin induces a greater incidence of disease. To further delineate epitopes of myosin heavy chain responsible for immunogenicity and disease, mice were immunized with fragments of genetically engineered rat alpha cardiac myosin. Epitopes in the region of difference between BALB/c and C57B/6 (residues 735-1032) induce disease in both susceptible and nonsusceptible mice. The data presented here demonstrate that pathogenic epitopes of both mouse and rat myosin residue in the polymorphic region of the S2 subunit. In addition, these studies suggest that polymorphisms in the autoantigen may be part of the genetic basis for autoimmune myocarditis.
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Affiliation(s)
- L Liao
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York 10461
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Raymond-Denise A, Sansonetti P, Guillén N. Identification and characterization of a myosin heavy chain gene (mhcA) from the human parasitic pathogen Entamoeba histolytica. Mol Biochem Parasitol 1993; 59:123-31. [PMID: 8515774 DOI: 10.1016/0166-6851(93)90013-n] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The mhcA gene from the human pathogen Entamoeba histolytica was identified using the polymerase chain reaction. It is a single copy gene expressed as a 6.4-kb mRNA. The deduced MhcA protein sequence is highly similar to myosin II from both Dictyostelium discoideum and Acanthamoeba castellanii. The globular head domain of MhcA contains the specific regions involved in ATP binding, actin binding, and interaction with myosin light chain. The tail domain is organized in an alpha-helical coiled coil structure, which suggests that MhcA is an alpha-fibrous protein. The coiled coil is interrupted by two prolines indicating that like other myosins, either from smooth muscle or from non-muscle cells, the tail of MhcA folds twice on itself. In addition, MhcA presents sequence similarities with the heavy chain phosphorylation sites of smooth and non-muscle vertebrate myosins.
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Affiliation(s)
- A Raymond-Denise
- Unité de Pathogénie Microbienne Moléculaire, U199 INSERM, Institut Pasteur, Paris, France
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11
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Vikstrom KL, Rovner AS, Saez CG, Bravo-Zehnder M, Straceski AJ, Leinwand LA. Sarcomeric myosin heavy chain expressed in nonmuscle cells forms thick filaments in the presence of substoichiometric amounts of light chains. CELL MOTILITY AND THE CYTOSKELETON 1993; 26:192-204. [PMID: 8293476 DOI: 10.1002/cm.970260303] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Central to the function of myosin is its ability to assemble into thick filaments which interact precisely and specifically with other myofibrillar proteins. We have established a novel experimental system for studying myofibrillogenesis using transient transfections of COS cells, a monkey kidney cell line. We have expressed both full-length rat alpha cardiac myosin heavy chain (MHC) and a truncated heavy meromyosin-like alpha MHC (sHMM) and shown that immunoreactive MHC proteins of the expected sizes were detected in lysates of transfected cells. Surprisingly, the full-length MHC formed large spindle-shaped structures throughout the cytoplasm of transfected cells as determined by immunofluorescence microscopy. The structures were not found in cells expressing the sHMM construct, indicating that their formation required an MHC rod. The spindle-shaped structures ranged in length from approximately 1 micron to over 20 microns in length and were birefringent suggesting that they are ordered arrays of thick filaments. This was confirmed by electron microscopic analysis of the transfected cells which revealed arrays of filamentous structures approximately 12 nm in diameter at their widest point. In addition, the vast majority of transfected MHC did not associate with the endogenous nonmuscle myosin light chains, demonstrating that myosin thick filaments can form in the absence of stoichiometric amounts of myosin light chains.
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Affiliation(s)
- K L Vikstrom
- Albert Einstein College of Medicine, Bronx, NY 10461-1975
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12
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Espreafico EM, Cheney RE, Matteoli M, Nascimento AA, De Camilli PV, Larson RE, Mooseker MS. Primary structure and cellular localization of chicken brain myosin-V (p190), an unconventional myosin with calmodulin light chains. J Cell Biol 1992; 119:1541-57. [PMID: 1469047 PMCID: PMC2289763 DOI: 10.1083/jcb.119.6.1541] [Citation(s) in RCA: 291] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Recent biochemical studies of p190, a calmodulin (CM)-binding protein purified from vertebrate brain, have demonstrated that this protein, purified as a complex with bound CM, shares a number of properties with myosins (Espindola, F. S., E. M. Espreafico, M. V. Coelho, A. R. Martins, F. R. C. Costa, M. S. Mooseker, and R. E. Larson. 1992. J. Cell Biol. 118:359-368). To determine whether or not p190 was a member of the myosin family of proteins, a set of overlapping cDNAs encoding the full-length protein sequence of chicken brain p190 was isolated and sequenced. Verification that the deduced primary structure was that of p190 was demonstrated through microsequence analysis of a cyanogen bromide peptide generated from chick brain p190. The deduced primary structure of chicken brain p190 revealed that this 1,830-amino acid (aa) 212,509-D) protein is a member of a novel structural class of unconventional myosins that includes the gene products encoded by the dilute locus of mouse and the MYO2 gene of Saccharomyces cerevisiae. We have named the p190-CM complex "myosin-V" based on the results of a detailed sequence comparison of the head domains of 29 myosin heavy chains (hc), which has revealed that this myosin, based on head structure, is the fifth of six distinct structural classes of myosin to be described thus far. Like the presumed products of the mouse dilute and yeast MYO2 genes, the head domain of chicken myosin-V hc (aa 1-764) is linked to a "neck" domain (aa 765-909) consisting of six tandem repeats of an approximately 23-aa "IQ-motif." All known myosins contain at least one such motif at their head-tail junctions; these IQ-motifs may function as calmodulin or light chain binding sites. The tail domain of chicken myosin-V consists of an initial 511 aa predicted to form several segments of coiled-coil alpha helix followed by a terminal 410-aa globular domain (aa, 1,421-1,830). Interestingly, a portion of the tail domain (aa, 1,094-1,830) shares 58% amino acid sequence identity with a 723-aa protein from mouse brain reported to be a glutamic acid decarboxylase. The neck region of chicken myosin-V, which contains the IQ-motifs, was demonstrated to contain the binding sites for CM by analyzing CM binding to bacterially expressed fusion proteins containing the head, neck, and tail domains. Immunolocalization of myosin-V in brain and in cultured cells revealed an unusual distribution for this myosin in both neurons and nonneuronal cells.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- E M Espreafico
- Department of Biology, Yale University, New Haven, Connecticut 06511
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13
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Saraswat L, Pastra-Landis S, Lowey S. Mapping single cysteine mutants of light chain 2 in chicken skeletal myosin. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)36804-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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14
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Pollenz RS, Chen TL, Trivinos-Lagos L, Chisholm RL. The Dictyostelium essential light chain is required for myosin function. Cell 1992; 69:951-62. [PMID: 1535025 DOI: 10.1016/0092-8674(92)90614-i] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A Dictyostelium mutant (7-11) that expresses less than 0.5% of wild-type levels of the myosin essential light chain (EMLC) has been created by overexpression of antisense RNA. Cells from 7-11 contain wild-type levels of the myosin heavy chain (MHC) and regulatory light chain (RMLC). Myosin isolated from 7-11 cells consists of the MHC with the RMLC associated in reduced stoichiometry, and binds to purified actin in an ATP-sensitive fashion. Purified 7-11 myosin displays calcium-activated ATPase activity with a Vmax about 15%-25% of that of wild type, and a Km for ATP of 27 +/- 5 microM versus 83 +/- 30 microM for wild type. At actin concentrations as high as 17 microM, 7-11 myosin displays greatly reduced actin-activated ATPase activity. Phenotypically, 7-11 cells resemble MHC mutants, growing poorly in suspension and becoming large and multinucleate. When starved for multicellular development, 7-11 cells take several hours longer than wild-type cells to aggregate. Although multicellular aggregates eventually form, they fail to develop further. The cells are also unable to cap receptors in response to Con A treatment. Since cells expressing the EMLC are phenotypically similar to MHC null mutants, the EMLC appears necessary for myosin function, at least in part because it is required for normal actin-activated ATPase activity.
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Affiliation(s)
- R S Pollenz
- Department of Cell, Molecular, and Structural Biology, Northwestern University Medical School, Chicago, Illinois 60611
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15
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Cornillon B, Cathiard AM, Eldin P, Anoal M, Cardinaud R, Liautard JP, Le Cunff M, Mornet D, Pons F, Leger J. Probing myosin light chain 1 structure with monoclonal antibodies. J Muscle Res Cell Motil 1992; 13:329-40. [PMID: 1527220 DOI: 10.1007/bf01766461] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Five monoclonal antibodies that react with different regions of myosin light chain 1 from human ventricular myocardial muscle were used to obtain information on interactions between the light chain 1 and heavy chains and generally on the tertiary structure of the light chain 1 within the myosin head. We performed Western blot assays of the five antibodies with myosins from different cardiac and skeletal muscles, with different proteolytic fragments of bovine ventricular myosin light chain 1 (LC1) and to different recombinant fragments of human ventricular LC1 and rat fast skeletal light chain LC1/LC3. The five antibodies were mapped in three different regions of the light chain 1: two antibodies mapped within the first eight amino-terminal residues, two between residues 71 and 74, and one between residues 129 and 134. The apparent dissociation constants of the last three antibodies, determined by antibody-antigen equilibria in solution, were lower than when isolated light chains were used as antigens. It is probable that the corresponding amino acids involved in the antibody epitopes were either involved in interactions between the light and heavy myosin subunits, or somehow hindered by the myosin heavy chain bulk. In contrast, the apparent dissociation constants measured for both other antibodies were higher when myosin, rather than isolated light chains, was used as antigen. Thus LC1 fixation to heavy chains within the myosin molecule induced conformation changes at the amino-terminal end of the light chain 1. No difference in the accessibility of this mobile LC1 segment was detected in the presence of actin. Finally, observed differences in epitope accessibility on the light chain LC1 in myosin, as compared with chymotryptic subfragment 1 (SF1), indicated conformational differences between native myosin and extensively studied SF1 molecules.
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Affiliation(s)
- B Cornillon
- Institut National de la Santé et de la Recherche Médicale U.300, Faculté de Pharmacie, Montpellier, France
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16
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Nozais M, Béchet JJ, Houadjeto M. Inactivation, subunit dissociation, aggregation, and unfolding of myosin subfragment 1 during guanidine denaturation. Biochemistry 1992; 31:1210-5. [PMID: 1531181 DOI: 10.1021/bi00119a034] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The effect of guanidine hydrochloride on ATPase activity, gel filtration, turbidity, exposure of thiol groups, far-UV circular dichroism, and the fluorescence emission intensity of myosin subfragment 1 (S-1) was studied under equilibrium conditions. It was found that the denaturation process involves several intermediate states. The enzymatic activity of S-1 is at first lost at very low concentrations of GdnHCl (lower than 0.5 M). At a slightly higher GdnHCl concentration (about 0.5 M), the light chains dissociate and this dissociation is closely followed by the formation of aggregates between the naked heavy chains of S-1 molecules in the guanidine hydrochloride range of concentrations 0.5-1 M. At GdnHCl concentrations above 1 M, aggregates gradually disappear and S-1 loses its secondary and tertiary structures. These phenomena are partly reversible, and ATPase activity is only partially recovered under highly limited conditions. These results are discussed in relation to the nature of myosin subunit assembly. The head fragment of 20 kDa is thus suggested to be implicated in the binding of light chain to heavy chain and in the self-association of free heavy chains.
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Affiliation(s)
- M Nozais
- Laboratoire de Biologie Physicochimique, Unité Associée au CNRS 1131, Orsay, France
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17
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Abstract
The unconventional myosins form a large and diverse group of molecular motors. The number of known unconventional myosins is increasing rapidly and in the past year alone two new classes have been identified. Substantial progress has been made towards characterizing the properties and functions of these motor proteins, which have been hypothesized to play fundamental roles in processes such as cell locomotion, phagocytosis and vesicle transport.
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Affiliation(s)
- R E Cheney
- Department of Biology, Yale University, New Haven, Connecticut 06511
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18
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Complete primary structure of a scallop striated muscle myosin heavy chain. Sequence comparison with other heavy chains reveals regions that might be critical for regulation. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)55085-7] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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