title: Structural basis for the in situ Ca(2+) sensitization of cardiac troponin C by positive feedback from force-generating myosin cross-bridges.
abstract: The in situ structural coupling between the cardiac troponin (cTn) Ca(2+)-sensitive regulatory switch (CRS) and strong myosin cross-bridges was investigated using Förster resonance energy transfer (FRET). The double cysteine mutant cTnC(T13C/N51C) was fluorescently labeled with the FRET pair 5-(iodoacetamidoethyl)aminonaphthelene-1-sulfonic acid (IAEDENS) and N-(4-dimethylamino-3,5-dinitrophenyl)maleimide (DDPM) and then incorporated into detergent skinned left ventricular papillary fiber bundles. Ca(2+) titrations of cTnC(T13C/N51C)AEDENS/DDPM-reconstituted fibers showed that the Ca(2+)-dependence of the opening of the N-domain of cTnC (N-cTnC) statistically matched the force-Ca(2+) relationship. N-cTnC opening still occurred steeply during Ca(2+) titrations in the presence of 1mM vanadate, but the maximal extent of ensemble-averaged N-cTnC opening and the Ca(2+)-sensitivity of the CRS were significantly reduced. At nanomolar, resting Ca(2+) levels, treatment with ADP·Mg in the absence of ATP caused a partial opening of N-cTnC. During subsequent Ca(2+) titrations in the presence of ADP·Mg and absence of ATP, further N-cTnC opening was stimulated as the CRS responded to Ca(2+) with increased Ca(2+)-sensitivity and reduced steepness. These findings supported our hypothesis here that strong cross-bridge interactions with the cardiac thin filament exert a Ca(2+)-sensitizing effect on the CRS by stabilizing the interaction between the exposed hydrophobic patch of N-cTnC and the switch region of cTnI.
authors.affiliation: Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164, USA.
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Rieck
authors.forename: King-Lun
authors.initials: KL
authors.lastname: Li
authors.forename: Yexin
authors.initials: Y
authors.lastname: Ouyang
authors.forename: R John
authors.initials: RJ
authors.lastname: Solaro
authors.forename: Wen-Ji
authors.initials: WJ
authors.lastname: Dong
mesh_terms: D000818:Animals; D002118:Calcium / Q000737:chemistry* / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology; D002478:Cells, Cultured; D025461:Feedback, Physiological / Q000502:physiology; D040542:Mechanotransduction, Cellular / Q000502:physiology; D009200:Myocardial Contraction / Q000502:physiology*; D009218:Myosins / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012518:Sarcomeres / Q000502:physiology*; D013314:Stress, Mechanical; D013329:Structure-Activity Relationship; D019209:Troponin C / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D019209:Troponin C; D009218:Myosins; D002118:Calcium
keywords: Cardiac muscle; Cardiac troponin; FRET; Myosin cross-bridges; Thin filament regulation
references.citation: Biochemistry. 2007 Aug 28;46(34):9752-61
references.pmid: 17676764
references.citation: Biophys J. 2000 Sep;79(3):1498-510
references.pmid: 10969011
references.citation: J Biomed Biotechnol. 2010;2010:105648
references.pmid: 20467475
references.citation: J Biol Chem. 1999 Jun 11;274(24):16681-4
references.pmid: 10358006
references.citation: Nature. 1982 Dec 23;300(5894):775-6
references.pmid: 6217425
references.citation: FEBS Lett. 1992 Oct 5;310(3):229-34
references.pmid: 1397278
references.citation: J Mol Biol. 2008 Jun 20;379(5):929-35
references.pmid: 18514658
references.citation: Physiol Rev. 2000 Apr;80(2):853-924
references.pmid: 10747208
references.citation: J Physiol. 1988 Jul;401:115-43
references.pmid: 3171985
references.citation: J Physiol. 2009 Jan 15;587(1):3
references.pmid: 19119179
references.citation: J Muscle Res Cell Motil. 2011 Nov;32(3):203-8
references.pmid: 21948173
references.citation: Circ Res. 2004 May 28;94(10):1290-300
references.pmid: 15166116
references.citation: J Mol Biol. 2004 Jul 2;340(2):295-305
references.pmid: 15201053
references.citation: J Physiol. 2002 Jul 1;542(Pt 1):221-9
references.pmid: 12096063
references.citation: J Appl Physiol (1985). 2000 Jan;88(1):180-5
references.pmid: 10642379
references.citation: Biochemistry. 1990 Aug 28;29(34):7982-90
references.pmid: 2261455
references.citation: Biochemistry. 2004 Aug 24;43(33):10642-52
references.pmid: 15311925
references.citation: J Biol Chem. 1987 Jun 5;262(16):7839-49
references.pmid: 3584144
references.citation: Eur J Biochem. 1989 Feb 1;179(2):373-8
references.pmid: 2537208
references.citation: Am J Physiol Regul Integr Comp Physiol. 2007 Oct;293(4):R1595-607
references.pmid: 17626127
references.citation: J Mol Cell Cardiol. 2010 May;48(5):859-65
references.pmid: 20004664
references.citation: Biochemistry. 2005 Jan 18;44(2):584-8
references.pmid: 15641783
references.citation: Circ Res. 2010 Mar 5;106(4):705-11
references.pmid: 20035081
references.citation: J Biol Chem. 2004 Jan 30;279(5):3535-42
references.pmid: 14594949
references.citation: J Mol Biol. 2001 Aug 31;311(5):1027-36
references.pmid: 11531337
references.citation: Biochemistry. 1988 Nov 1;27(22):8408-15
references.pmid: 2977286
references.citation: J Biol Chem. 1999 Oct 29;274(44):31382-90
references.pmid: 10531339
references.citation: Biophys J. 2000 Jun;78(6):3103-11
references.pmid: 10827987
references.citation: Biophys J. 2008 Nov 15;95(10):4772-89
references.pmid: 18676638
references.citation: J Physiol. 2009 Jan 15;587(1):155-63
references.pmid: 19015190
references.citation: J Physiol. 1988 Dec;407:489-503
references.pmid: 3151492
references.citation: Physiology (Bethesda). 2007 Apr;22:73-80
references.pmid: 17420299
references.citation: Biochemistry. 2008 Dec 16;47(50):13383-93
references.pmid: 19053249
references.citation: J Biol Chem. 2012 Mar 2;287(10):7661-74
references.pmid: 22207765
references.citation: Biochemistry. 1991 Jan 29;30(4):958-65
references.pmid: 1824926
references.citation: Curr Cardiol Rev. 2009 May;5(2):119-24
references.pmid: 20436852
references.citation: Proc Natl Acad Sci U S A. 2008 Jul 29;105(30):10372-7
references.pmid: 18658238
references.citation: Nat New Biol. 1972 Jul 26;238(82):97-101
references.pmid: 4261616
references.citation: Biochemistry. 2013 Mar 19;52(11):1950-62
references.pmid: 23425245
references.citation: FASEB J. 2008 Apr;22(4):1246-57
references.pmid: 17984178
references.citation: Biophys J. 1995 Apr;68(4):1430-42
references.pmid: 7787029
references.citation: J Physiol. 2007 Apr 15;580(Pt. 2):561-76
references.pmid: 17317743
references.citation: J Mol Biol. 1997 Feb 14;266(1):8-14
references.pmid: 9054965
references.citation: J Muscle Res Cell Motil. 2004;25(7):559-79
references.pmid: 15711886
references.citation: Biochemistry. 1999 Jun 29;38(26):8289-98
references.pmid: 10387074
references.citation: Anal Biochem. 2005 Dec 15;347(2):303-15
references.pmid: 16289079
references.citation: Biophys J. 2009 May 6;96(9):3692-702
references.pmid: 19413974
references.citation: J Biol Chem. 2009 Jun 12;284(24):16432-16441
references.pmid: 19369252
references.citation: Biophys J. 2007 May 1;92(9):3195-206
references.pmid: 17293397
references.citation: Biophys J. 2011 Feb 2;100(3):665-674
references.pmid: 21281581
references.citation: Biophys J. 1993 Aug;65(2):693-701
references.pmid: 8218897
references.citation: Biochemistry. 1992 Aug 11;31(31):7190-7
references.pmid: 1386527
references.citation: J Mol Biol. 2006 Aug 25;361(4):625-33
references.pmid: 16876196
references.citation: Annu Rev Physiol. 2005;67:39-67
references.pmid: 15709952
references.citation: Science. 1983 Mar 4;219(4588):1075-7
references.pmid: 6823567
references.citation: Biochemistry. 1997 Oct 7;36(40):12138-46
references.pmid: 9315850
references.citation: Arch Biochem Biophys. 2013 Jul 1;535(1):56-67
references.pmid: 23246786