Evidence that F-actin can hydrolyze ATP independent of monomer-polymer end interactions.
Evidence that F-actin can hydrolyze ATP independent of monomer-polymer end interactions.
复制标题
有证据表明 F-肌动蛋白可以独立于单体-聚合物末端相互作用来水解 ATP。
DOI：
10.1016/s0021-9258(17)43426-0
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发表时间：
1984
期刊：
影响因子：
--
通讯作者：
E. Korn
中科院分区：
文献类型：
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作者：
S. Brenner;E. Korn
AMP和ADP可抑制F-肌动蛋白在50 mM KC_1、0.1 mM CaC_(12)溶液中稳态时的ATP水解率。AMP的KI为9微米，ADP的KI为44微米。1 mM AMP对ATP水解酶的抑制率大于95%。AMP对肌动蛋白聚合的时间进程、聚合过程中的ATP水解以及肌动蛋白的临界浓度没有影响。G-肌动蛋白/F-肌动蛋白亚基交换和核苷酸交换的同时测量表明，核苷酸交换发生得比亚基交换快得多；在实验过程中，当F-肌动蛋白亚基交换不到1%时，超过50%的F-肌动蛋白结合的核苷酸被替换。当AMP存在时，它被结合到聚合物中，防止ADP从溶液中的ATP中掺入。结合了镁离子的F-肌动蛋白对AMP的敏感性远低于结合了钙离子的F-肌动蛋白。这些数据提供了与溶液中F-肌动蛋白结合的ADP直接交换为游离ATP相关的ATP水解循环的证据，而不依赖于单体-聚合物末端的相互作用。当Ca~(2+)与F-肌动蛋白前体结合时，核苷酸的这种交换和水解可能会增强。
The rate of ATP hydrolysis in solutions of F-actin at steady state in 50 mM KC1, 0.1 mM CaC12 was inhibited by AMP and ADP. The inhibition was competitive with ATP (Km of about 600 microM) with Ki values of 9 microM for AMP and 44 microM for ADP. ATP hydrolysis was inhibited greater than 95% by 1 mM AMP. AMP had no effect on the time course of actin polymerization, ATP hydrolysis during polymerization, or the critical actin concentration. Simultaneous measurements of G-actin/F-actin subunit exchange and nucleotide exchange showed that nucleotide exchange occurred much more rapidly than subunit exchange; during the experiment over 50% of the F-actin-bound nucleotide was replaced when less than 1% of the F-actin subunits had exchanged. When AMP was present it was incorporated into the polymer, preventing incorporation of ADP from ATP in solution. F-actin with bound Mg2+ was much less sensitive to AMP than F-actin with bound Ca2+. These data provide evidence for an ATP hydrolysis cycle associated with direct exchange of F-actin-bound ADP for ATP free in solution independent of monomer-polymer end interactions. This exchange and hydrolysis of nucleotide may be enhanced when Ca2+ is bound to the F-actin protomers.