Coleman T R, Mooseker M S
J Cell Biol. 1985 Nov;101(5 Pt 1):1850-7. doi: 10.1083/jcb.101.5.1850.
We have used two actin-binding proteins of the intestinal brush border, TW 260/240 and villin, to examine the effects of filament cross-linking and filament length on myosin-actin interactions. TW 260/240 is a nonerythroid spectrin that is a potent cross-linker of actin filaments. In the presence of this cross-linker we observed a concentration-dependent enhancement of skeletal muscle actomyosin ATPase activity (150-560% of control; maximum enhancement at a 1:70-80 TW 260/240:actin molar ratio). TW 260/240 did not cause a similar enhancement of either acto-heavy meromyosin (HMM) ATPase or acto-myosin subfragment-one (S1) ATPase. Villin, a Ca2+-dependent filament capping and severing protein of the intestinal microvillus, was used to generate populations of actin filaments of various lengths from less than 20 nm to 2.0 microns; (villin:actin ratios of 1:2 to 1:4,000). The effect of filament length on actomyosin ATPase was biphasic. At villin:actin molar ratios of 1:2-25 actin-activated myosin ATPase activity was inhibited to 20-80% of control values, with maximum inhibition observed at the highest villin:actin ratio. The ATPase activities of acto-HMM and acto-S1 were also inhibited at these short filament lengths. At intermediate filament lengths generated at villin:actin ratios of 1:40-400 (average lengths 0.26-1.1 micron) an enhancement of actomyosin ATPase was observed (130-260% of controls), with a maximum enhancement at average filament lengths of 0.5 micron. The levels of actomyosin ATPase fell off to control values at low concentrations of villin where filament length distributions were almost those of controls. Unlike intact myosin, the actin-activated ATPase of neither HMM nor S1 showed an enhancement at these intermediate actin filament lengths.
我们使用了两种肠刷状缘的肌动蛋白结合蛋白，TW 260/240和绒毛蛋白，来研究细丝交联和细丝长度对肌球蛋白-肌动蛋白相互作用的影响。TW 260/240是一种非红细胞血影蛋白，是肌动蛋白丝的有效交联剂。在这种交联剂存在的情况下，我们观察到骨骼肌肌动球蛋白ATP酶活性呈浓度依赖性增强（为对照的150%-560%；在TW 260/240与肌动蛋白的摩尔比为1:70-80时增强最大）。TW 260/240不会引起肌动蛋白-重酶解肌球蛋白（HMM）ATP酶或肌动蛋白-肌球蛋白亚片段-1（S1）ATP酶的类似增强。绒毛蛋白是一种依赖Ca2+的肠微绒毛细丝封端和切断蛋白，用于产生长度从小于20纳米到2.0微米不等的各种肌动蛋白丝群体；（绒毛蛋白与肌动蛋白的比例为1:2至1:4000）。细丝长度对肌动球蛋白ATP酶的影响是双相的。在绒毛蛋白与肌动蛋白的摩尔比为1:2-25时，肌动蛋白激活的肌球蛋白ATP酶活性被抑制至对照值的20%-80%，在最高的绒毛蛋白与肌动蛋白比例时观察到最大抑制。在这些短细丝长度下，肌动蛋白-HMM和肌动蛋白-S1的ATP酶活性也受到抑制。在绒毛蛋白与肌动蛋白比例为1:40-400时产生的中等细丝长度（平均长度0.26-1.1微米）下，观察到肌动球蛋白ATP酶增强（为对照的130%-260%），在平均细丝长度为0.5微米时增强最大。在低浓度绒毛蛋白时，肌动球蛋白ATP酶水平降至对照值，此时细丝长度分布几乎与对照相同。与完整的肌球蛋白不同，HMM和S1的肌动蛋白激活的ATP酶在这些中等肌动蛋白细丝长度下均未显示增强。
