Okagaki Tsuyoshi, Takami Masaki, Hosokawa Kiyo, Yano Miyuki, Higashi-Fujime Sugie, Ooi Atsushi
Department of Bioresources, Mie University, Kamihama 1515, Tsu, Mie 514-8507, Japan.
J Biochem. 2005 Sep;138(3):255-62. doi: 10.1093/jb/mvi121.
Two types of myosin isolated from ordinary (fast) and dark (slow) muscles of carp were examined by ATPase and in vitro motility assays. Vmax of the ATPase activity and sliding velocity of ordinary myosin showed 1.6 and 1.5 times higher activities than those of dark myosin, whereas those of mammalian fast myosin were much higher, 3 to 10 times, than those of slow myosin. Although ordinary myosin had almost identical activities to those of mammalian fast myosin, activities of dark myosin was twice of those of mammalian slow myosin. This high motile activity of dark myosin can account for the physiological role of dark muscle in cruising of fish. By comparing Km of the actin-activated ATPase activity, ordinary myosin was appeared to have higher affinity to F-actin than dark myosin, and this was confirmed by the binding assay of HMM or S-1 of carp myosin to F-actin. Investigation of myosin assembly by electron microscopy and the centrifugation assay revealed that ordinary myosin assembled much poorly than dark myosin or mammalian fast myosin. This phenomenon may reflect characteristic cellular function of fish skeletal muscle.
通过ATP酶和体外运动分析，对从鲤鱼的普通（快）肌和暗色（慢）肌中分离出的两种肌球蛋白进行了检测。普通肌球蛋白的ATP酶活性的Vmax和滑动速度比暗色肌球蛋白分别高1.6倍和1.5倍，而哺乳动物快肌肌球蛋白的Vmax和滑动速度比慢肌肌球蛋白高得多，是其3到10倍。尽管普通肌球蛋白的活性与哺乳动物快肌肌球蛋白几乎相同，但暗色肌球蛋白的活性却是哺乳动物慢肌肌球蛋白的两倍。暗色肌球蛋白的这种高运动活性可以解释暗色肌在鱼类巡游中的生理作用。通过比较肌动蛋白激活的ATP酶活性的Km值，发现普通肌球蛋白对F-肌动蛋白的亲和力高于暗色肌球蛋白，鲤鱼肌球蛋白的重酶解肌球蛋白（HMM）或轻酶解肌球蛋白（S-1）与F-肌动蛋白的结合试验证实了这一点。通过电子显微镜和离心分析对肌球蛋白组装的研究表明，普通肌球蛋白的组装能力比暗色肌球蛋白或哺乳动物快肌肌球蛋白差得多。这种现象可能反映了鱼类骨骼肌的特征性细胞功能。
