蜜蜂间接飞翔肌粗肌丝的微丝结构

用能溶解肌球蛋白但不溶解副肌球蛋白的溶液(300 mM KCI,pH6.0)处理分离的蜜蜂间接飞翔肌粗肌丝,经数分钟后可以看到粗肌丝端头散开成为多根微丝,微丝数最多为7根。延长处理时间,可以见到粗肌丝中央部分只剩下直径约为5 nm的徽丝。实验结果支持我们以前提出的蜜蜂间接飞翔肌粗肌丝的结构模式,并指示贯穿肌小节、两端都和Z线相连的内芯至少部分由副肌球蛋白组成。只存在于A带的,由6根微丝形成的外套是由肌球蛋白分子组成。

THE SUBFILAMENT STRUCTURE OF THE THICK MYOFILAMENT OF THE HONEY BEE INDIRECT FLIGHT MUSCLE

In 1966 WR proposed a model for the thick myofilament of the honey bee indirect flight muscle. It was suggested that the thick myofilament was composed of a central core, extending from Z to Z line and a mantle, composed of probably six rod-shaped protein subfilaments. In this article, we provide further experimental evidences for this model. Bight minutes after treating the isolated thick myofilam-ents with 300 mM KG1 (pII 6.0) solution, which can only dissolve myosin but not paraanyosin, the terminal portion of the myofilaonent might separate into 7 subfilaments. Prolonging the time of treatment would cause the diameter of the middle portion of the thick myofilame'nt to reduce to only about 5 ma. The length of the segment of the myofilament being thinned increased with increasing the time of treatment. These results further indicate that the core of the thick myofilament is at least partly composed of paramyosin and the man-tal is composed of six myosin subfilaments.