scholarly journals Single Cardiac Ventricular Myosins Change Step-Size with Loading

2017 ◽  
Author(s):  
Yihua Wang ◽  
Chen-Ching Yuan ◽  
Katarzyna Kazmierczak ◽  
Danuta Szczesna-Cordary ◽  
Thomas P. Burghardt
Keyword(s):  
Actin Binding ◽  
Transgenic Mouse Models ◽  
Cardiac Myosin ◽  
Step Size ◽  
Average Force ◽  
Essential Light Chain ◽  
C Terminus ◽  
N Terminus ◽  
Mutant Forms ◽  
Increasing Load

ABSTRACTThe cardiac myosin motor powers the beating heart by catalyzed ATPase free energy conversion to contractile work. Transgenic mouse models for heart disease express mouse α-cardiac myosin heavy chain with human essential light chain (ELC) in wild type (WT), or hypertrophic cardiomyopathy linked mutant forms, A57G or E143K. Mutants modify the ELC actin binding N-terminus or C-terminus regions. Motility and single myosin mechanical characteristics show stark contrasts between the motors related to their average force, power, and displacement while all indicate the ability to down-shift ensemble step-size with increasing load. A57G and E143K consume more ATP than control WT in the presence of actin with A57G upregulating and E143K downregulating power compared with WT. Higher ATP consumption and downregulated power in E143K implies a lower unitary force. Effects on power are consistent with an A57G that impairs the ELC N-terminus actin binding and an E143K that reduces lever-arm rigidity.

scholarly journals Single cardiac ventricular myosins are autonomous motors

Open Biology ◽  
2018 ◽  
Vol 8 (4) ◽  
pp. 170240 ◽  
Author(s):  
Yihua Wang ◽  
Chen-Ching Yuan ◽  
Katarzyna Kazmierczak ◽  
Danuta Szczesna-Cordary ◽  
Thomas P. Burghardt
Keyword(s):  
Actin Binding ◽  
Control Force ◽  
Cardiac Myosin ◽  
Step Size ◽  
Size Selection ◽  
Essential Light Chain ◽  
N Terminus ◽  
Increasing Load

Myosin transduces ATP free energy into mechanical work in muscle. Cardiac muscle has dynamically wide-ranging power demands on the motor as the muscle changes modes in a heartbeat from relaxation, via auxotonic shortening, to isometric contraction. The cardiac power output modulation mechanism is explored in vitro by assessing single cardiac myosin step-size selection versus load. Transgenic mice express human ventricular essential light chain (ELC) in wild- type (WT), or hypertrophic cardiomyopathy-linked mutant forms, A57G or E143K, in a background of mouse α-cardiac myosin heavy chain. Ensemble motility and single myosin mechanical characteristics are consistent with an A57G that impairs ELC N-terminus actin binding and an E143K that impairs lever-arm stability, while both species down-shift average step-size with increasing load. Cardiac myosin in vivo down-shifts velocity/force ratio with increasing load by changed unitary step-size selections. Here, the loaded in vitro single myosin assay indicates quantitative complementarity with the in vivo mechanism. Both have two embedded regulatory transitions, one inhibiting ADP release and a second novel mechanism inhibiting actin detachment via strain on the actin-bound ELC N-terminus. Competing regulators filter unitary step-size selection to control force-velocity modulation without myosin integration into muscle. Cardiac myosin is muscle in a molecule.

scholarly journals N-Terminus of Cardiac Myosin Essential Light Chain Modulates Myosin Step-Size

Biochemistry ◽  
2015 ◽  
Vol 55 (1) ◽  
pp. 186-198 ◽  
Author(s):  
Yihua Wang ◽  
Katalin Ajtai ◽  
Katarzyna Kazmierczak ◽  
Danuta Szczesna-Cordary ◽  
Thomas P. Burghardt
Keyword(s):  
Light Chain ◽  
Cardiac Myosin ◽  
Step Size ◽  
Essential Light Chain ◽  
N Terminus

scholarly journals Cardiac Myosin Essential Light Chain N-Terminus Regulates Motor Step-Size

2015 ◽  
Vol 108 (2) ◽  
pp. 598a
Author(s):  
Yihua Wang ◽  
Katalin Ajtai ◽  
Katarzyna Kazmierczak ◽  
Danuta Szczesna-Cordary ◽  
Thomas P. Burghardt
Keyword(s):  
Light Chain ◽  
Cardiac Myosin ◽  
Step Size ◽  
Essential Light Chain ◽  
N Terminus

scholarly journals Structure of the N Terminus of a Nonmuscle α-Tropomyosin in Complex with the C Terminus: Implications for Actin Binding†‡

Biochemistry ◽  
2009 ◽  
Vol 48 (6) ◽  
pp. 1272-1283 ◽  
Author(s):  
Norma J. Greenfield ◽  
Lucy Kotlyanskaya ◽  
Sarah E. Hitchcock-DeGregori
Keyword(s):  
Actin Binding ◽  
C Terminus ◽  
N Terminus

Actopaxin is phosphorylated during mitosis and is a substrate for cyclin B1/cdc2 kinase

2002 ◽  
Vol 363 (2) ◽  
pp. 233-242 ◽  
Author(s):  
Michael CURTIS ◽  
Sotiris N. NIKOLOPOULOS ◽  
Christopher E. TURNER
Keyword(s):  
Cell Division ◽  
Focal Adhesions ◽  
Cyclin B1 ◽  
Actin Binding ◽  
Phosphorylation Sites ◽  
Cdc2 Kinase ◽  
C Terminus ◽  
N Terminus ◽  
Focal Adhesion Protein

Prior to cell division, normal adherent cells adopt a round morphology that is associated with a loss of actin stress fibres and disassembly of focal adhesions. In this study, we investigate the mitotic phosphorylation of the recently described paxillin and actin-binding focal-adhesion protein actopaxin [Nikolopoulos and Turner (2000) J. Cell Biol. 151, 1435–1448]. Actopaxin is comprised of an N-terminus containing six putative cdc2 phosphorylation sites and a C-terminus consisting of tandem calponin homology domains. Here we show that the N-terminus of actopaxin is phosphorylated by cyclin B1/cdc2 kinase in vitro and that this region of actopaxin precipitates cdc2 kinase activity from mitotic lysates. Actopaxin exhibits reduced electrophoretic mobility during mitosis that is dependent on phosphorylation within the first two consensus cdc2 phosphorylation sites. Finally, as cells progress from mitosis to G1 there is an adhesion-independent dephosphorylation of actopaxin, suggesting that actopaxin dephosphorylation precedes cell spreading and the reformation of focal adhesions. Taken together, these results suggest a role for cyclin B1/cdc2-dependent phosphorylation of actopaxin in regulating actin cytoskeleton reorganization during cell division.

scholarly journals Cardiac and skeletal actin substrates uniquely tune cardiac myosin strain-dependent mechanics

Open Biology ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 180143 ◽  
Author(s):  
Yihua Wang ◽  
Katalin Ajtai ◽  
Thomas P. Burghardt
Keyword(s):  
Step Size ◽  
Actin Isoforms ◽  
Essential Light Chain ◽  
Cardiac Actin ◽  
N Terminus ◽  
Human Adults ◽  
Force Velocity ◽  
Strain Dependent

Cardiac ventricular myosin (βmys) translates actin by transducing ATP free energy into mechanical work during muscle contraction. Unitary βmys translation of actin is the step-size. In vitro and in vivo βmys regulates contractile force and velocity autonomously by remixing three different step-sizes with adaptive stepping frequencies. Cardiac and skeletal actin isoforms have a specific 1 : 4 stoichiometry in normal adult human ventriculum. Human adults with inheritable hypertrophic cardiomyopathy (HCM) upregulate skeletal actin in ventriculum probably compensating the diseased muscle's inability to meet demand by adjusting βmys force–velocity characteristics. βmys force–velocity characteristics were compared for skeletal versus cardiac actin substrates using ensemble in vitro motility and single myosin assays. Two competing myosin strain-sensitive mechanisms regulate step-size choices dividing single βmys mechanics into low- and high-force regimes. The actin isoforms alter myosin strain-sensitive regulation such that onset of the high-force regime, where a short step-size is a large or major contributor, is offset to higher loads probably by the unique cardiac essential light chain (ELC) N-terminus/cardiac actin contact at Glu6/Ser358. It modifies βmys force–velocity by stabilizing the ELC N-terminus/cardiac actin association. Uneven onset of the high-force regime for skeletal versus cardiac actin modulates force–velocity characteristics as skeletal/cardiac actin fractional content increases in diseased muscle.

Preparation and properties of three analogues of [5-leucine]enkephalin, substrates for enzyme conversion studies

1985 ◽  
Vol 50 (6) ◽  
pp. 1329-1334
Author(s):  
Jaroslav Vičar ◽  
Linda Servítová ◽  
Martin Flegel ◽  
Karel Hauzer ◽  
Tomislav Barth
Keyword(s):  
High Pressure ◽  
Liquid Chromatography ◽  
Guinea Pig ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Guinea Pig Ileum ◽  
Opioid Activity ◽  
C Terminus ◽  
N Terminus ◽  
Fragment Condensation

Analogues of [5-Leu]enkephalin, prolonged by methionine on the N-terminus or, by lysine or methionine on the C-terminus were prepared by fragment condensation, purified by ion exchange chromatography or high-pressure liquid chromatography. The substances were characterised by their opioid activity in a test on guinea-pig ileum in comparison with the activity of [5-Leu]enkephalin.

scholarly journals C-Terminal Deletions Can Suppress Temperature-Sensitive Mutations and Change Dominance in the Phage Mu Repressor

Genetics ◽  
1996 ◽  
Vol 142 (3) ◽  
pp. 661-672 ◽  
Author(s):  
Jodi L Vogel ◽  
Vincent Geuskens ◽  
Lucie Desmet ◽  
N Patrick Higgins ◽  
Ariane Toussaint
Keyword(s):  
Binding Activity ◽  
Temperature Sensitive ◽  
Dna Binding Activity ◽  
Heat Stable ◽  
C Terminus ◽  
Acid Domain ◽  
Mutant Forms ◽  
Amino Acid Domain

Abstract Mutations in an N-terminal 70-amino acid domain of bacteriophage Mu's repressor cause temperature-sensitive DNA-binding activity. Surprisingly, amber mutations can conditionally correct the heat-sensitive defect in three mutant forms of the repressor gene, cts25 (D43-G), cts62 (R47-Q and cts71 (M28-I), and in the appropriate bacterial host produce a heat-stable Sts phenotype (for survival of temperature shifts). Sts repressor mutants are heat sensitive when in supE or supF hosts and heat resistant when in Sup° hosts. Mutants with an Sts phenotype have amber mutations at one of three codons, Q179, Q187, or Q190. The Sts phenotype relates to the repressor size: in Sup° hosts sts repressors are shorter by seven, 10, or 18 amino acids compared to repressors in supE or supF hosts. The truncated form of the sts62-1 repressor, which lacks 18 residues (Q179–V196), binds Mu operator DNA more stably at 42° in vitro compared to its full-length counterpart (cts62 repressor). In addition to influencing temperature sensitivity, the C-terminus appears to control the susceptibility to in vivo Clp proteolysis by influencing the multimeric structure of repressor.

Sign in / Sign up

Export Citation Format

Share Document