Vigoreaux J O
Department of Zoology, University of Vermont, Burlington 05405-0086.
Biochem Genet. 1994 Aug;32(7-8):301-14. doi: 10.1007/BF00555832.
Flightin is a 20-kD myofibrillar protein found in the stretch-activated flight muscles of Drosophila melanogaster. Nine of the eleven isoelectric variants of flightin are generated in vivo by multiple phosphorylations. The accumulation of these isoelectric variants is affected differently by mutations that eliminate thick filaments or thin filaments. Mutations in the myosin heavy-chain gene that prevent thick filament assembly block accumulation of all flightin variants except N1, the unphosphorylated precursor, which is present at much reduced levels. Mutations in the flight muscle-specific actin gene that block actin synthesis and prevent thin filament assembly disrupt the temporal regulation of flightin phosphorylation, resulting in premature phosphorylation and premature accumulation of flightin phosphovariants. Cellular fractionation of fibers that are devoid of thin filaments show that flightin remains associated with the thick filament-rich cytomatrix. These results suggest that flightin is a structural component of the thick filaments whose regulated phosphorylation is dependent upon the presence of thin filaments.
肌动蛋白结合蛋白（Flightin）是一种20千道尔顿的肌原纤维蛋白，存在于黑腹果蝇的牵张激活飞行肌肉中。肌动蛋白结合蛋白的11种等电变体中有9种是在体内通过多次磷酸化产生的。这些等电变体的积累受到消除粗肌丝或细肌丝的突变的不同影响。肌球蛋白重链基因中的突变阻止粗肌丝组装，除了未磷酸化的前体N1外，所有肌动蛋白结合蛋白变体的积累均受阻，而N1的水平大幅降低。飞行肌肉特异性肌动蛋白基因中的突变阻止肌动蛋白合成并防止细肌丝组装，从而破坏了肌动蛋白结合蛋白磷酸化的时间调控，导致肌动蛋白结合蛋白磷酸变体的过早磷酸化和过早积累。对缺乏细肌丝的纤维进行细胞分级分离表明，肌动蛋白结合蛋白仍与富含粗肌丝的细胞基质相关。这些结果表明，肌动蛋白结合蛋白是粗肌丝的一种结构成分，其磷酸化调控依赖于细肌丝的存在。
