2 COFACTORS AND CYTOPLASMIC CHAPERONIN ARE REQUIRED FOR THE FOLDING OF ALPHA-TUBULIN AND BETA-TUBULIN
2 COFACTORS AND CYTOPLASMIC CHAPERONIN ARE REQUIRED FOR THE FOLDING OF ALPHA-TUBULIN AND BETA-TUBULIN
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DOI：
10.1128/mcb.13.4.2478
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发表时间：
1993-04-01
影响因子：
5.3
通讯作者：
COWAN, NJ
中科院分区：
文献类型：
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作者：
GAO, YI;VAINBERG, IE;COWAN, NJ
虽然在原核生物，线粒体和叶绿体中介导折叠的伴侣蛋白已经相对较好地表征，但在真核细胞质溶胶中蛋白质的折叠还不太清楚。我们最近鉴定了一种细胞质伴侣蛋白，它是一种800 kDa的多亚基环状体，与未折叠的肌动蛋白形成二元复合物;正确折叠的多肽在与Mg-ATP孵育后释放（Y。高，J. O.托马斯河L.周，G. - H. Lee和N. J.科万，细胞69：1043 - 1050，1992）。在这里，我们表明，同样的伴侣蛋白也形成了一个二元复合物与未折叠的α-或β-微管蛋白，但是，没有检测到释放的正确折叠的产品，无论添加的Mg-ATP和Mg-GTP的浓度或添加的载体微管蛋白异二聚体的存在下，新折叠的α-或β-微管蛋白多肽可能会交换。相反，需要两个额外的蛋白质辅因子来产生正确折叠的α-或β-微管蛋白，然后其能够交换成预先存在的α/β-微管蛋白异二聚体。我们发现，肌动蛋白和微管蛋白相互竞争有效地与细胞质伴侣复合物的协会。这些数据表明，肌动蛋白和α-和β-微管蛋白与伴侣蛋白复合物上的相同位点相互作用。
Though the chaperonins that mediate folding in prokaryotes, mitochondria, and chloroplasts have been relatively well characterized, the folding of proteins in the eukaryotic cytosol is much less well understood. We recently identified a cytoplasmic chaperonin as an 800-kDa multisubunit toroid which forms a binary complex with unfolded actin; the correctly folded polypeptide is released upon incubation with Mg-ATP (Y. Gao, J. O. Thomas, R. L. Chow, G.-H. Lee, and N. J. Cowan, Cell 69:1043-1050, 1992). Here we show that the same chaperonin also forms a binary complex with unfolded alpha- or beta-tubulin; however, there is no detectable release of the correctly folded product, irrespective of the concentration of added Mg-ATP and Mg-GTP or the presence of added carrier tubulin heterodimers with which newly folded alpha- or beta-tubulin polypeptides might exchange. Rather, two additional protein cofactors are required for the generation of properly folded alpha- or beta-tubulin, which is then competent for exchange into preexisting alpha/beta-tubulin heterodimers. We show that actin and tubulins compete efficiently with one another for association with cytoplasmic chaperonin complexes. These data imply that actin and alpha- and beta-tubulin interact with the same site(s) on chaperonin complexes.