Berger C L, Craik J S, Trentham D R, Corrie J E, Goldman Y E
Pennsylvania Muscle Institute, University of Pennsylvania, Philadelphia 19104, USA.
Biophys J. 1995 Apr;68(4 Suppl):78S-80S.
We have used fluorescence polarization to examine orientational changes of the 5- and 6-isomers of acetamidotetramethylrhodamine (ATR) covalently bound to SH-1 (Cys-707 of the myosin heavy chain) in single, skinned fibers from rabbit psoas muscle after rapid length steps or photolysis of caged nucleotides. Similar results were obtained with both the 5- and 6-isomers of ATR. After the photolysis of caged ATP, large and rapid changes in the fluorescence polarization signals were observed and were complete well before appreciable force had been generated. Changes in the fluorescence polarization signals after the photolysis of caged ADP were similar to those after the photolysis of caged ATP, despite an almost negligible change in force. The fluorescence polarization signals remained almost constant after rapid length steps in both rigor and active muscle fibers. These results suggest that structural changes at SH-1 monitored by 5- or 6-ATR are not associated directly with the force-generating event of muscle contraction, but may be involved in the communication pathway between the nucleotide and actin-binding sites of myosin.
我们利用荧光偏振来检测与兔腰大肌单根去表皮肌纤维中SH-1（肌球蛋白重链的半胱氨酸707）共价结合的乙酰氨基四甲基罗丹明（ATR）的5-异构体和6-异构体在快速长度变化或笼锁核苷酸光解后的取向变化。ATR的5-异构体和6-异构体都得到了类似的结果。笼锁ATP光解后，观察到荧光偏振信号发生了大而快速的变化，且在产生明显力量之前就已完全完成。笼锁ADP光解后的荧光偏振信号变化与笼锁ATP光解后的相似，尽管力量变化几乎可以忽略不计。在强直和活动肌纤维中，快速长度变化后荧光偏振信号几乎保持不变。这些结果表明，通过5-或6-ATR监测的SH-1处的结构变化与肌肉收缩的力量产生事件没有直接关联，但可能参与了肌球蛋白核苷酸结合位点和肌动蛋白结合位点之间的信号传导途径。
