Chalovich J M, Greene L E, Eisenberg E
Proc Natl Acad Sci U S A. 1983 Aug;80(16):4909-13. doi: 10.1073/pnas.80.16.4909.
Myosin subfragment 1 (S-1) with its two reactive cysteine groups crosslinked by N,N'-p-phenylenedimaleimide (pPDM), is shown to be a stable analogue of S-1 X ATP and S-1 X ADP X Pi, the predominant complexes present during the steady-state hydrolysis of ATP by S-1. pPDM-S-1 binds to actin with about twice the affinity of S-1 X ATP or S-1 X ADP X Pi, whereas its affinity is 1/100th of that of S-1 X 5'-adenylyl imidodiphosphate and 1/1,000th of that of S-1 X ADP. pPDM-S-1 is also similar to S-1 X ATP and S-1 X ADP X Pi in that its binding to actin is not inhibited by troponin-tropomyosin. In contrast, the binding of S-1, S-1 X ADP, and S-1 X 5'-adenylyl imidodiphosphate to actin is markedly inhibited by troponin-tropomyosin in the absence of Ca2+ when actin is in large excess over S-1. This suggests that modifying S-1 with pPDM stabilizes a conformation which mimics that induced by the binding of ATP.
肌球蛋白亚片段1（S-1）的两个反应性半胱氨酸基团通过N，N'-对苯二甲酰亚胺马来酰亚胺（pPDM）交联，结果表明它是S-1·ATP和S-1·ADP·Pi的稳定类似物，这两种复合物是S-1在ATP稳态水解过程中存在的主要复合物。pPDM-S-1与肌动蛋白结合的亲和力约为S-1·ATP或S-1·ADP·Pi的两倍，而其亲和力是S-1·5'-腺苷酰亚胺二磷酸的1/100，是S-1·ADP的1/1000。pPDM-S-1与肌动蛋白的结合也不受肌钙蛋白-原肌球蛋白的抑制，这一点与S-1·ATP和S-1·ADP·Pi相似。相比之下，当肌动蛋白大大过量于S-1时，在没有Ca2+的情况下，肌钙蛋白-原肌球蛋白会显著抑制S-1、S-1·ADP和S-1·5'-腺苷酰亚胺二磷酸与肌动蛋白的结合。这表明用pPDM修饰S-1可稳定一种模拟ATP结合诱导的构象。
