title: Ventricular myosin modifies in vitro step-size when phosphorylated.
abstract: Cardiac and skeletal muscle myosins have the central role in contraction transducing ATP free energy into the mechanical work of moving actin. Myosin has a motor domain containing ATP and actin binding sites and a lever-arm that undergoes rotation impelling bound actin. The lever-arm converts torque generated in the motor into the linear displacement known as step-size. The myosin lever-arm is stabilized by bound essential and regulatory light chains (ELC and RLC). RLC phosphorylation at S15 is linked to modified lever-arm mechanical characteristics contributing to myosin filament based contraction regulation and to the response of the muscle to disease. Myosin step-size was measured using a novel quantum dot (Qdot) assay that previously confirmed a 5nm step-size for fast skeletal myosin and multiple unitary steps, most frequently 5 and 8nm, and a rare 3nm displacement for β cardiac myosin (βMys). S15 phosphorylation in βMys is now shown to change step-size distribution by advancing the 8nm step frequency. After phosphorylation, the 8nm step is the dominant myosin step-size resulting in significant gain in the average step-size. An increase in myosin step-size will increase the amount of work produced per ATPase cycle. The results indicate that RLC phosphorylation modulates work production per ATPase cycle suggesting the mechanism for contraction regulation by the myosin filament.
authors.affiliation: Department of Biochemistry and Molecular Biology, United States.
authors.forename: Yihua
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Biochemistry and Molecular Biology, United States.
authors.forename: Katalin
authors.initials: K
authors.lastname: Ajtai
authors.affiliation: Department of Biochemistry and Molecular Biology, United States; Department of Physiology and Biomedical Engineering, United States. Electronic address: burghardt@mayo.edu.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Burghardt
mesh_terms: D000199:Actins / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001696:Biomechanical Phenomena; D002465:Cell Movement; D006352:Heart Ventricles / Q000737:chemistry / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism; D009200:Myocardial Contraction / Q000502:physiology*; D009206:Myocardium / Q000378:metabolism; D018994:Myosin Light Chains / Q000378:metabolism*; D010766:Phosphorylation; D045663:Quantum Dots; D011817:Rabbits; D013552:Swine; D024723:Ventricular Myosins / Q000378:metabolism*
chemical_list: D000199:Actins; D018994:Myosin Light Chains; D000255:Adenosine Triphosphate; D024723:Ventricular Myosins
keywords: Actin-activated ATPase; Cardiac myosin RLC phosphorylation; In vitro motility; Qdot assay; Ventricular myosin step-size
references.citation: Proc Natl Acad Sci U S A. 2004 Jul 27;101(30):10973-8
references.pmid: 15256600
references.citation: J Mol Biol. 2009 Apr 3;387(3):706-25
references.pmid: 19361417
references.citation: Nat Genet. 2006 May;38(5):561-5
references.pmid: 16642020
references.citation: Biochemistry. 2013 Feb 19;52(7):1249-59
references.pmid: 23343568
references.citation: J Biol Chem. 1993 Sep 25;268(27):20414-8
references.pmid: 8376398
references.citation: J Biol Chem. 1984 Apr 25;259(8):5045-53
references.pmid: 6715335
references.citation: Biochim Biophys Acta. 2007 May;1773(5):615-30
references.pmid: 16904206
references.citation: Nat Methods. 2010 May;7(5):339-40
references.pmid: 20431545
references.citation: Proc Natl Acad Sci U S A. 2010 Oct 5;107(40):17403-8
references.pmid: 20855589
references.citation: J Clin Invest. 2012 Apr;122(4):1209-21
references.pmid: 22426213
references.citation: J Mol Cell Cardiol. 2010 Feb;48(2):286-92
references.pmid: 19799913
references.citation: Biochemistry. 2001 Oct 9;40(40):12078-93
references.pmid: 11580283
references.citation: FASEB J. 2009 Oct;23(10):3571-80
references.pmid: 19470801
references.citation: Methods Enzymol. 1982;85 Pt B:164-81
references.pmid: 7121269
references.citation: Neuromuscul Disord. 2007 May;17(5):355-67
references.pmid: 17434305
references.citation: Arch Biochem Biophys. 2011 Jun 15;510(2):120-8
references.pmid: 21284933
references.citation: Arch Biochem Biophys. 2011 Jun 15;510(2):129-34
references.pmid: 21345328
references.citation: Cardiovasc Res. 1998 Feb;37(2):381-404
references.pmid: 9614495
references.citation: Methods Enzymol. 2012;504:183-200
references.pmid: 22264535
references.citation: Biochemistry. 2002 Apr 30;41(17):5429-38
references.pmid: 11969403
references.citation: J Physiol. 1999 Sep 15;519 Pt 3:669-78
references.pmid: 10457082
references.citation: Biochemistry. 2013 Mar 5;52(9):1611-21
references.pmid: 23383646
references.citation: Appl Opt. 1989 Dec 15;28(24):5237-42
references.pmid: 20556034
references.citation: J Physiol. 2010 Mar 15;588(Pt 6):981-93
references.pmid: 20123786
references.citation: J Mol Med (Berl). 1999 Jul;77(7):544-55
references.pmid: 10494800
references.citation: Am J Physiol Heart Circ Physiol. 2013 Jan 15;304(2):H253-9
references.pmid: 23144314
references.citation: Circ Res. 1998 Jun 1;82(10):1029-34
references.pmid: 9622155
references.citation: Biochem Biophys Res Commun. 2011 Dec 16;416(3-4):367-71
references.pmid: 22120626
references.citation: J Biol Chem. 2013 May 10;288(19):13446-54
references.pmid: 23530050
references.citation: Proc Natl Acad Sci U S A. 2001 Dec 18;98(26):14949-54
references.pmid: 11734631
references.citation: Am J Physiol Regul Integr Comp Physiol. 2009 Aug;297(2):R265-74
references.pmid: 19458282