Functional divergence between co-chaperones of Hsc70
Functional divergence between co-chaperones of Hsc70
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DOI：
10.1074/jbc.m803923200
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发表时间：
2008-10-03
影响因子：
4.8
通讯作者：
Young, Jason C.
中科院分区：
文献类型：
--
作者：
Tzankov, Stefan;Wong, Michael J. H.;Young, Jason C.
分子伴侣Hsc 70的ATP酶循环受辅分子伴侣的调节; Hsp 40/DnaJ相关蛋白刺激Hsc 70的ATP水解，并且可以结合未折叠的多肽本身。相反，各种核苷酸交换因子（NEF）刺激Hsc 70的ADP-ATP交换。我们分析了纯化的Hsp 40相关的共伴侣DJA 1（Hdj 2）和DJA 2（Hdj 3），发现它们与一系列多肽具有不同的结合模式。DJA 2单独可以刺激Hsc 70介导的荧光素酶在NEF的情况下的重折叠，而DJA 1活性低得多。Bag 1 NEF的加入增加了Hsc 70和DJA 2的重折叠，新表征的NEF Hsp 110也是如此，但每种NEF与Hsc 70的最佳浓度比不同。值得注意的是，NEF HspBP 1在任何浓度下都不能增加Hsc 70和DJA 2的重折叠，并且没有NEF改善DJA 1的重折叠活性。相反，DJA 1抑制DJA 2和Hsc 70的重折叠。DJA 1或DJA 2与三种NEFs的所有组合都刺激了Hsc 70 ATP酶速率，尽管Hsp 110随着浓度的增加变得不那么有效。嵌合体DJA 2具有Hsc 70刺激性J结构域，其被DJA 1的J结构域取代，该嵌合体DJA 2具有Hsc 70的多肽结合和ATP酶刺激功能。然而，它不能支持有效的Hsc 70介导的重折叠，也抑制DJA 2和Hsc 70的重折叠。这些结果表明Hsc 70机制的模型比以前认为的更复杂，Hsc 70共分子伴侣之间具有显著的功能差异。
The ATPase cycle of the chaperone Hsc70 is regulated by co-chaperones; Hsp40/DnaJ-related proteins stimulate ATP hydrolysis by Hsc70 and can bind unfolded polypeptides themselves. Conversely, various nucleotide exchange factors (NEFs) stimulate ADP-ATP exchange by Hsc70. We analyzed the purified Hsp40-related co-chaperones DJA1 (Hdj2) and DJA2 (Hdj3) and found that they had a distinct pattern of binding to a range of polypeptides. DJA2 alone could stimulate Hsc70-mediated refolding of luciferase in the absence of NEF, whereas DJA1 was much less active. The addition of the Bag1 NEF increased refolding by Hsc70 and DJA2, as did the newly characterized NEF Hsp110, but each NEF had a different optimal concentration ratio to Hsc70. Notably, the NEF HspBP1 could not increase refolding by Hsc70 and DJA2 at any concentration, and none of the NEFs improved the refolding activity with DJA1. Instead, DJA1 was inhibitory of refolding with DJA2 and Hsc70. All combinations of DJA1 or DJA2 with the three NEFs stimulated the Hsc70 ATPase rate, although Hsp110 became less effective with increasing concentrations. A chimeric DJA2 having its Hsc70-stimulatory J domain replaced with that of DJA1 was functional for polypeptide binding and ATPase stimulation of Hsc70. However, it could not support efficient Hsc70-mediated refolding and also inhibited refolding with DJA2 and Hsc70. These results suggest a more complex model of Hsc70 mechanism than has been previously thought, with notable functional divergence between Hsc70 co- chaperones.