title: Hypertrophic cardiomyopathy-linked mutation D145E drastically alters calcium binding by the C-domain of cardiac troponin C.
abstract: The role of the C-domain sites of cardiac troponin C in the modulation of the calcium signal remains unclear. In this study, we investigated the effects of hypertrophic cardiomyopathy-linked mutations A8V, E134D, and D145E in cardiac troponin C on the properties of the C-domain sites. The A8V mutation had essentially no effect on the calcium or magnesium binding properties of the C-domain sites, while the mutation E134D moderately decreased calcium and magnesium binding affinities. On the other hand, the D145E mutation affected cooperative interactions between sites III and IV, significantly reducing the calcium binding affinity of both sites. Binding of the anchoring region of cardiac troponin I (corresponding to residues 34-71) to cardiac troponin C with the D145E mutation was not able to recover normal calcium binding to the C-domain. Experiments utilizing the fluorescent hydrophobic probe bis-ANS suggest that the D145E mutation dramatically reduced the extent of calcium-induced hydrophobic exposure by the C-domain. At high nonphysiological calcium concentration, A8V, E134D, and D145E mutations minimally affected the affinity of cardiac troponin C for the regulatory region of cardiac troponin I (corresponding to residues 128-180). In contrast, at lower physiological calcium concentration, the D145E mutation led to an approximately 8-fold decrease in the affinity of cardiac troponin C for the regulatory region of cardiac troponin I. Our results suggest that calcium binding properties of the C-domain sites might be important for the proper regulatory function of cardiac troponin C.
authors.affiliation: Department of Pharmacological and Pharmaceutical Sciences, University of Houston, Houston, Texas 77004, USA.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Swindle
authors.forename: Svetlana B
authors.initials: SB
authors.lastname: Tikunova
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics*; D001224:Aspartic Acid / Q000235:genetics; D002118:Calcium / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020013:Calcium Signaling / Q000235:genetics / Q000502:physiology; D002312:Cardiomyopathy, Hypertrophic / Q000235:genetics* / Q000378:metabolism; D018698:Glutamic Acid / Q000235:genetics; D006801:Humans; D008274:Magnesium / Q000378:metabolism; D009119:Muscle Contraction / Q000235:genetics; D009154:Mutation; D011485:Protein Binding / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D019209:Troponin C / Q000378:metabolism*
chemical_list: D019209:Troponin C; D001224:Aspartic Acid; D018698:Glutamic Acid; D008274:Magnesium; D002118:Calcium
references.citation: Nature. 2003 Jul 3;424(6944):35-41
references.pmid: 12840750
references.citation: J Biol Chem. 2004 Apr 23;279(17):17348-60
references.pmid: 14970231
references.citation: Arch Biochem Biophys. 1995 Oct 20;323(1):115-9
references.pmid: 7487056
references.citation: Biochem Biophys Res Commun. 1975 May 5;64(1):122-7
references.pmid: 1170846
references.citation: J Biol Chem. 1980 Dec 25;255(24):11688-93
references.pmid: 6449512
references.citation: Biochemistry. 1997 Mar 25;36(12):3608-16
references.pmid: 9132012
references.citation: J Mol Cell Cardiol. 2008 Aug;45(2):281-8
references.pmid: 18572189
references.citation: Int J Biochem Cell Biol. 2006 Jan;38(1):110-22
references.pmid: 16183325
references.citation: Cell Res. 2003 Feb;13(1):9-20
references.pmid: 12643345
references.citation: J Biol Chem. 1996 Apr 5;271(14):8381-6
references.pmid: 8626536
references.citation: Biochemistry. 2002 May 28;41(21):6697-705
references.pmid: 12022873
references.citation: Biometals. 1998 Dec;11(4):297-318
references.pmid: 10191495
references.citation: J Pharmacol Sci. 2006;100(5):525-37
references.pmid: 16799263
references.citation: Clin Biochem. 2009 Jun;42(9):755-65
references.pmid: 19318019
references.citation: Cardiovasc Res. 2008 Mar 1;77(4):619-26
references.pmid: 18079104
references.citation: Biochemistry. 2010 Mar 2;49(8):1719-26
references.pmid: 20104876
references.citation: J Biol Chem. 1992 Jan 15;267(2):825-31
references.pmid: 1530938
references.citation: J Biol Chem. 1993 Nov 15;268(32):24067-73
references.pmid: 8226952
references.citation: Biochemistry. 2010 Mar 9;49(9):1975-84
references.pmid: 20128626
references.citation: Biochemistry. 2000 Aug 1;39(30):8782-90
references.pmid: 10913289
references.citation: Biochemistry (Mosc). 1999 Sep;64(9):969-85
references.pmid: 10521712
references.citation: FASEB J. 1995 Jun;9(9):755-67
references.pmid: 7601340
references.citation: J Biol Chem. 2002 Dec 20;277(51):49716-26
references.pmid: 12397067
references.citation: J Mol Cell Cardiol. 2010 May;48(5):882-92
references.pmid: 19914256
references.citation: J Biol Chem. 1996 Jan 12;271(2):817-23
references.pmid: 8557691
references.citation: J Hum Genet. 2003;48(2):55-64
references.pmid: 12601548
references.citation: Biochemistry. 2003 Dec 16;42(49):14460-8
references.pmid: 14661957
references.citation: Proteins. 1999 Nov 15;37(3):499-507
references.pmid: 10591109
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: J Biol Chem. 2004 Aug 20;279(34):35341-52
references.pmid: 15205455
references.citation: Biophys J. 2007 May 1;92(9):3195-206
references.pmid: 17293397
references.citation: J Biol Chem. 2004 Nov 26;279(48):49579-87
references.pmid: 15358779
references.citation: Annu Rev Physiol. 2005;67:39-67
references.pmid: 15709952
references.citation: J Biol Chem. 1997 Jul 18;272(29):18216-21
references.pmid: 9218458
references.citation: J Biol Chem. 2009 Jul 10;284(28):19090-100
references.pmid: 19439414
references.citation: Hum Mol Genet. 2002 Oct 1;11(20):2499-506
references.pmid: 12351586
references.citation: Biochem J. 2007 Jul 15;405(2):199-221
references.pmid: 17590154