A myopathy-linked tropomyosin mutation severely alters thin filament conformational changes during activation.
Human point mutations in beta- and gamma-tropomyosin induce contractile deregulation, skeletal muscle weakness, and congenital myopathies. The aim of the present study was to elucidate the hitherto unknown underlying molecular mechanisms. Hence, we recorded and analyzed the X-ray diffraction patterns of human membrane-permeabilized muscle cells expressing a particular beta-tropomyosin mutation (R133W) associated with a loss in cell force production, in vivo muscle weakness, and distal arthrogryposis. Upon addition of calcium, we notably observed less intensified changes, compared with controls, (i) in the second (1/19 nm(-1)), sixth (1/5.9 nm(-1)), and seventh (1/5.1 nm(-1)) actin layer lines of cells set at a sarcomere length, allowing an optimal thin-thick filament overlap; and (ii) in the second actin layer line of overstretched cells. Collectively, these results directly prove that during activation, switching of a positive to a neutral charge at position 133 in the protein partially hinders both calcium- and myosin-induced tropomyosin movement over the thin filament, blocking actin conformational changes and consequently decreasing the number of cross-bridges and subsequent force production.
Ochala
Julien
J
Department of Neuroscience, Clinical Neurophysiology, Uppsala University, Uppsala, Sweden. julien.ochala@neuro.uu.se
Iwamoto
Hiroyuki
H
Larsson
Lars
L
Yagi
Naoto
N
D008841:Actin Cytoskeleton / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D009135:Muscular Diseases / Q000235:genetics*; D009154:Mutation; D013314:Stress, Mechanical; D014335:Tropomyosin / Q000737:chemistry* / Q000235:genetics; D014961:X-Ray Diffraction
D014335:Tropomyosin
Bioessays. 1991 Sep;13(9):429-37
1796905
Biophys J. 2003 Feb;84(2 Pt 1):1093-102
12547790
Biophys J. 1998 Mar;74(3):1452-64
9512041
Biochemistry. 2003 Dec 9;42(48):14114-21
14640678
Biochemistry. 2002 Dec 17;41(50):15036-44
12475253
Hum Mol Genet. 2009 Jul 1;18(13):2359-69
19346529
J Physiol. 1986 Aug;377:487-505
3795099
J Biol Chem. 1997 Jan 31;272(5):2583-6
9053397
Adv Exp Med Biol. 1988;226:369-80
3261488
J Physiol. 1993 Dec;472:595-614
8145163
J Mol Biol. 2009 Jul 3;390(1):99-111
19433094
J Mol Biol. 1989 Jul 20;208(2):359-63
2769764
Biophys J. 1994 Nov;67(5):1984-93
7858135
J Mol Biol. 1975 Oct 25;98(2):293-304
1195389
Muscle Nerve. 1997 Aug;20(8):948-52
9236784
Biophys J. 2003 Oct;85(4):2492-506
14507712
J Mol Biol. 1973 Mar 25;75(1):33-55
4713300
J Muscle Res Cell Motil. 2001;22(1):5-49
11563548
Neurology. 2007 Mar 6;68(10):772-5
17339586
Structure. 2006 Jan;14(1):43-50
16407064
Adv Exp Med Biol. 2008;644:95-109
19209816
Nature. 2002 Feb 7;415(6872):659-62
11832949
J Biol Chem. 1999 Aug 6;274(32):22191-6
10428784
Proc Natl Acad Sci U S A. 2001 Jul 17;98(15):8496-501
11438684
J Mol Biol. 2008 Nov 28;383(5):1019-36
18817786
J Mol Biol. 2001 Jan 26;305(4):863-74
11162098
J Physiol. 2003 Jul 1;550(Pt 1):205-15
12730342
J Mol Biol. 2002 Apr 12;317(5):707-20
11955019
Biophys J. 2009 Feb;96(3):1045-55
19186142
J Physiol. 1979 Jul;292:177-92
314975
J Physiol. 1979 Jun;291:143-59
314510
J Biol Chem. 2000 Jul 21;275(29):22470-8
10801864
J Physiol. 2007 Jun 15;581(Pt 3):1283-92
17430991
J Mol Med (Berl). 2008 Nov;86(11):1197-204
18574571