期刊
JOURNAL OF PHYSIOLOGY-LONDON
卷 588, 期 24, 页码 5105-5114出版社
WILEY
DOI: 10.1113/jphysiol.2010.199067
关键词
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资金
- Uppsala University
- Swedish National Centre for Research in Sports (CIF) [143/10]
- Swedish Medical Research Council [08651]
- European Commission (MyoAge, EC) [CT-223756, COST CM1001]
Muscle, motor unit and muscle fibre type-specific differences in force-generating capacity have been investigated for many years, but there is still no consensus regarding specific differences between slow- and fast-twitch muscles, motor units or muscle fibres. This is probably related to a number of different confounding factors disguising the function of the molecular motor protein myosin. We have therefore studied the force-generating capacity of specific myosin isoforms or combination of isoforms extracted from short single human muscle fibre segments in a modified single fibre myosin in vitro motility assay, in which an internal load (actin-binding protein) was added in different concentrations to evaluate the force-generating capacity. The force indices were the x-axis intercept and the slope of the relationship between the fraction of moving filaments and the alpha-actinin concentration. The force-generating capacity of the beta/slow myosin isoform (type I) was weaker (P < 0.05) than the fast myosin isoform (type II), but the force-generating capacity of the different human fast myosin isoforms types IIa and IIx or a combination of both (IIax) were indistinguishable. A single fibre in vitro motility assay for both speed and force of specific myosin isoforms is described and used to measure the difference in force-generating capacity between fast and slow human myosin isoforms. The assay is proposed as a useful tool for clinical studies on the effects on muscle function of specific mutations or post-translational modifications of myosin.
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