馬骨格筋ミオシンの分子構築に関する研究

Horse skeletal muscle myosin was isolated from nine distinct muscles; transverse pectoral, gluteus medius, extensor carpi radialis, gastrocnemius, descending pectoral, internal intercostal, longus coli, diaphragm and masseter.<br>The light and heavy chain subunits of myosin were focused on to determine their predisposition to associate with fast or slow twitch fibers and the impact of their specific distribution.<br>A 15% SDS separating gel in Tris buffer was used for light chain, and for heavy chain study 5% gels with 25% glycerol. Proteins were quantitated with a laser-beam densitometer (LKB) connected to a computer programmed integrator.<br>The result showed that extensor carpi radialis and gastrocnemius were typical fast twitch muscles, as evidence by the preponderance of fast-twitch fibers in heavy chains (>90% HC_f) and light chains (100% LC_1f+LC_2f). Descending pectoral (D. P.) and internal intercostal (I. I.) can be classified as intermediate with a much greater content of fast-twitch light chains LC_1f and LC_2f, than of slow-twitch light chains LC_1s and LC_2s. The masseter can be classified as typical slow-twitch muscle on the basis of light and heavy chain composition. Longus coilli and diaphragm were also intermediate with respect to light chain composition, containing LC_1s and its isoform and LC_2s as well as LC_1f, however, heavy chains comprised only slow-twitch fibers (100% HC_s). Internal intercostal, extensor carpi radialis and diaphragm contain an isoform of LC_1s. Both I. I. and D. P. contain almost equal portions of HC_f, and HC_s. The transverse pectoral and gluteus medius can be classified as fast-twitch muscle on the basis of the predominance of the LC_1f and LC_2f subunits and the appearance of detectable amounts of LC_3f. Almost 100% of the 2 heavy chains in these muscles were HC_f. The diversity found in chain distribution among skeletal muscle myosin from a single horse was unexpected.