The E117K mutation in β-tropomyosin disturbs concerted conformational changes of actomyosin in muscle fibers.

Olga E Karpicheva, Charles S Redwood, Yurii S Borovikov

Archives of biochemistry and biophysics 2014 May 1

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The effect of the skeletal myopathy-causing E117K mutation in human β-tropomyosin on actomyosin structure during the ATPase cycle was studied using fluorescent probes bound to actin subdomain 1 and the myosin head. Multistep changes in flexural rigidity of actin filament and in spatial arrangement of actin subdomain 1 and myosin SH1 helix in troponin-free ghost muscle fibers were revealed. During the ATPase cycle E117K tropomyosin inhibited the rotation of subdomain 1 by 46% and the tilt of the SH1 helix by 49% compared with wild-type. At strong-binding stages the proportion of strong binding sub-states in the actomyosin population is decreased by the mutation. At weak-binding stages abnormally high numbers of switched-on actin monomers were observed, thus indicating a disturbance in concerted conformational changes of actomyosin. These structural alterations are likely to underlie the contractile deficit observed with this mutation. Copyright © 2014 Elsevier Inc. All rights reserved.

Citation

Olga E Karpicheva, Charles S Redwood, Yurii S Borovikov. The E117K mutation in β-tropomyosin disturbs concerted conformational changes of actomyosin in muscle fibers. Archives of biochemistry and biophysics. 2014 May 1;549:12-6