title: The influence of myosin converter and relay domains on cross-bridge kinetics of Drosophila indirect flight muscle.
abstract: We are investigating the influence of the converter and relay domains on elementary rate constants of the actomyosin cross-bridge cycle. The converter and relay domains vary between Drosophila myosin heavy chain isoforms due to alternative mRNA splicing. Previously, we found that separate insertions of embryonic myosin isoform (EMB) versions of these domains into the indirect flight muscle (IFM) myosin isoform (IFI) both decreased Drosophila IFM power and slowed muscle kinetics. To determine cross-bridge mechanisms behind the changes, we employed sinusoidal analysis while varying phosphate and MgATP concentrations in skinned Drosophila IFM fibers. Based on a six-state cross-bridge model, the EMB converter decreased myosin rate constants associated with actin attachment and work production, k(4), but increased rates related to cross-bridge detachment and work absorption, k(2). In contrast, the EMB relay domain had little influence on kinetics, because only k(4) decreased. The main alteration was mechanical, in that work production amplitude decreased. That both domains decreased k(4) supports the hypothesis that these domains are critical to lever-arm-mediated force generation. Neither domain significantly influenced MgATP affinity. Our modeling suggests the converter domain is responsible for the difference in rate-limiting cross-bridge steps between EMB and IFI myosin--i.e., a myosin isomerization associated with MgADP release for EMB and Pi release for IFI.
authors.affiliation: Department of Biology and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York, USA.
authors.forename: Chaoxing
authors.initials: C
authors.lastname: Yang
authors.forename: Charlotte N
authors.initials: CN
authors.lastname: Kaplan
authors.forename: Maria L
authors.initials: ML
authors.lastname: Thatcher
authors.forename: Douglas M
authors.initials: DM
authors.lastname: Swank
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D029721:Drosophila Proteins / Q000737:chemistry* / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000378:metabolism* / Q000502:physiology; D005426:Flight, Animal; D007700:Kinetics; D008958:Models, Molecular; D018482:Muscle, Skeletal / Q000378:metabolism*; D009218:Myosins / Q000737:chemistry* / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D017434:Protein Structure, Tertiary
chemical_list: D029721:Drosophila Proteins; D010710:Phosphates; D020033:Protein Isoforms; D000255:Adenosine Triphosphate; D009218:Myosins
references.citation: Circ Res. 2002 Jan 11;90(1):66-72
references.pmid: 11786520
references.citation: News Physiol Sci. 1999 Jun;14:87-92
references.pmid: 11390828
references.citation: Cell Mol Life Sci. 2005 Jul;62(13):1462-77
references.pmid: 15924264
references.citation: Philos Trans R Soc Lond B Biol Sci. 2004 Dec 29;359(1452):1819-28
references.pmid: 15647158
references.citation: Adv Exp Med Biol. 1993;332:567-77; discussion 577-80
references.pmid: 8109368
references.citation: J Mol Biol. 2006 Jan 20;355(3):432-42
references.pmid: 16325202
references.citation: Curr Biol. 1997 Feb 1;7(2):R112-8
references.pmid: 9081660
references.citation: Adv Protein Chem. 2005;71:161-93
references.pmid: 16230112
references.citation: Biophys J. 2004 Sep;87(3):1805-14
references.pmid: 15345559
references.citation: Biophys J. 2002 Feb;82(2):915-28
references.pmid: 11806933
references.citation: Proc Natl Acad Sci U S A. 2005 May 10;102(19):6873-8
references.pmid: 15863618
references.citation: Pflugers Arch. 1989 May;414(1):73-81
references.pmid: 2726438
references.citation: Microsc Res Tech. 2000 Sep 15;50(6):430-42
references.pmid: 10998634
references.citation: Cell. 1998 Sep 4;94(5):559-71
references.pmid: 9741621
references.citation: Biophys J. 2007 Mar 1;92(5):1623-31
references.pmid: 17142278
references.citation: J Mol Biol. 2008 Jun 6;379(3):443-56
references.pmid: 18462751
references.citation: J Mol Biol. 2009 Jun 19;389(4):707-21
references.pmid: 19393244
references.citation: Proc Natl Acad Sci U S A. 2002 Mar 19;99(6):3557-62
references.pmid: 11904418
references.citation: Soc Gen Physiol Ser. 1982;37:109-30
references.pmid: 6983138
references.citation: Biophys J. 1995 Aug;69(2):524-37
references.pmid: 8527667
references.citation: J Biol Chem. 2003 Dec 12;278(50):50293-300
references.pmid: 14506231
references.citation: Mol Cell Biol. 1989 Jul;9(7):2957-74
references.pmid: 2506434
references.citation: Biophys J. 2006 Apr 1;90(7):2427-35
references.pmid: 16399836
references.citation: J Muscle Res Cell Motil. 1980 Sep;1(3):279-303
references.pmid: 6971874
references.citation: Am J Physiol Cell Physiol. 2003 Apr;284(4):C1031-8
references.pmid: 12477668
references.citation: Biophys J. 2007 Aug 1;93(3):760-9
references.pmid: 17496022
references.citation: J Biol Chem. 2001 Jun 1;276(22):19491-4
references.pmid: 11278776
references.citation: Proc Natl Acad Sci U S A. 2006 Nov 14;103(46):17543-7
references.pmid: 17085600
references.citation: J Biol Chem. 2000 Nov 24;275(47):37167-72
references.pmid: 10945998
references.citation: Nat Cell Biol. 2003 Nov;5(11):980-6
references.pmid: 14578909
references.citation: J Mol Biol. 2007 Mar 23;367(2):591-602
references.pmid: 17275022
references.citation: Science. 1993 Jul 2;261(5117):58-65
references.pmid: 8316858
references.citation: Mech Dev. 2001 Mar;101(1-2):35-45
references.pmid: 11231057
references.citation: Biophys J. 2005 Nov;89(5):3248-60
references.pmid: 16143633
references.citation: J Mol Biol. 1997 Aug 8;271(1):1-6
references.pmid: 9300050
references.citation: Biophys J. 1997 Dec;73(6):3122-34
references.pmid: 9414224
references.citation: J Biol Chem. 2007 Jun 15;282(24):17658-64
references.pmid: 17449872
references.citation: Biophys J. 2009 Aug 5;97(3):806-24
references.pmid: 19651039
references.citation: J Biol Chem. 2001 Dec 7;276(49):45902-8
references.pmid: 11590173
references.citation: Biophys J. 2008 Dec;95(11):5228-37
references.pmid: 18805920
references.citation: Nature. 1983 Mar 31-Apr 6;302(5907):393-7
references.pmid: 6403869
references.citation: J Gen Physiol. 1982 Aug;80(2):279-97
references.pmid: 6981684
references.citation: Nat Cell Biol. 2002 Apr;4(4):312-6
references.pmid: 11901423
references.citation: Biochemistry. 2003 Jan 14;42(1):90-5
references.pmid: 12515542