Kinetic properties of myosin heavy chain isoforms in mouse skeletal muscle: comparison with rat, rabbit, and human and correlation with amino acid sequence

Abstract

Galler. Kinetic properties of myosin heavy chain isoforms in mouse skeletal muscle: comparison with rat, rabbit, and human and correlation with amino acid sequence. Am J Physiol Cell Physiol 287: C1725-C1732, 2004. First published August 11, 2004 doi:10.1152/ ajpcell.00255.2004.-Stretch activation kinetics were investigated in skinned mouse skeletal muscle fibers of known myosin heavy chain (MHC) isoform content to assess kinetic properties of different myosin heads while generating force. The time to peak of stretchinduced delayed force increase (t3) was strongly correlated with MHC isoforms [t3 given in ms for fiber types containing specified isoforms; means Ϯ SD with n in parentheses: MHCI 680 Ϯ 108 (13) For rat, rabbit, and human skeletal muscles the same type of correlation was found previously. The kinetics decreases slightly with increasing body mass. Available amino acid sequences were aligned to quantify the structural variability of MHC isoforms of different animal species. The variation in t3 showed a correlation with the structural variability of specific actin-binding loops (so-called loop 2 and loop 3) of myosin heads (r ϭ 0.74). This suggests that alterations of amino acids in these loops contribute to the different kinetics of myosin heads of various MHC isoforms.isoform structure-function relationship; stretch activation; muscle mechanics SKELETAL MUSCLES ARE COMPOSED of different fiber types to fulfill various functional needs. This diversity relates to the existence of specific myofibrillar protein isoforms in different fiber types (for review, see Refs. 41 and 46). Muscle fiber types are generally categorized according to their specific myosin heavy chain (MHC) isoforms. The head portion of this protein is the essential component of the force-generating mechanism of muscle (for review, see Ref. 30). Three fast fiber types (type II) have been identified in limb muscles of adult rodents: types IIB, IIX (or IID), and IIA, containing the isoforms MHCIIb, MHCIIx(d), and MHCIIa, respectively. Conversely, only one slow fiber type (type I) has to date been characterized by its MHC isoform, called MHCI, but there is increasing evidence that the type I fibers do not represent a homogeneous population (2,11,15).MHC isoform content determines the contractile properties of muscle fibers (for review see Ref. 4). The relation between MHC content, stretch activation kinetics, and unloaded shortening velocity (V u ) has been clearly established for rat, rabbit, and human skeletal muscle fibers (4,7,9,17,35). Although the mouse is the most important mammalian model for genetic manipulations, the skeletal muscle fibers of this species have been investigated to a much lesser degree. The relationship between shortening velocity and load has been determined in different mouse muscle fiber types. Furthermore, V u was compared with the actin filament sliding propelled by the different myosin isoforms (28, 39). The kinetics of stretch activation has never been investigated in mouse skeletal muscle fibers, although a...

Fine-tuning of cross-bridge kinetics in cardiac muscle of rat and mouse by myosin light chain isoforms

“…These force transients seem to be due to a synchronization of a fraction of myosin heads by the rapid change in the fiber length. This assumption is supported by the finding that the kinetics of force transients shows a conspicuous correlation with the MHC isoform content of skeletal and cardiac muscle preparations [3,4,[11][12][13]. Stepwise stretches result in a simultaneous force increase followed by a force decay and a delayed force increase (stretch activation [12,13,16]).…”

Scaling of skeletal muscle shortening velocity in mammals representing a 100,000-fold difference in body size

“…The MyHC isoform expressed is the most important factor in determining V 0 in both skeletal and cardiac muscle [6]. Further evidence suggests that the specific actin-binding loops (loops 2 and 3) play a critical role in determining the differences in V 0 between fiber types and species [3]. Differences between skeletal and cardiac muscle contractile function are further modified by the regulatory proteins.…”

Skeletal muscle fiber types in the ghost crab,Ocypode quadrata:implications for running performance

“…More recently, the common occurrence of these fibers has called this interpretation into question, raising the possibility that these intermediate fibers types provide a continuum of mechanical properties to the muscles (Caiozzo et al, 2003;Medler et al, 2004;Stephenson, 2001). Indeed, single fibers containing two MHC isoforms possess contractile properties intermediate to pure fiber types (Andruchov et al, 2004;Caiozzo, 2002;Caiozzo et al, 2003). In the case of the mid-region fibers in the extensor and flexor carpopodite, it is unclear what advantage might be gained by the roughly equal expression of two isoforms, rather than expressing a single isoform.…”