Felts S J, Owen B A, Nguyen P, Trepel J, Donner D B, Toft D O
Department of Biochemistry, Mayo Graduate School, Rochester, Minnesota 55905, USA.
J Biol Chem. 2000 Feb 4;275(5):3305-12. doi: 10.1074/jbc.275.5.3305.
The hsp90 family of molecular chaperones was expanded recently due to the cloning of TRAP1 and hsp75 by yeast two-hybrid screens. Careful analysis of the human TRAP1 and hsp75 sequences revealed that they are identical, and we have cloned a similar protein from Drosophila. Immunofluorescence data show that human TRAP1 is localized to mitochondria. This mitochondrial localization is supported by the existence of mitochondrial localization sequences in the amino termini of both the human and Drosophila proteins. Due to the striking homology of TRAP1 to hsp90, we tested the ability of TRAP1 to function as an hsp90-like chaperone. TRAP1 did not form stable complexes with the classic hsp90 co-chaperones p23 and Hop (p60). Consistent with these observations, TRAP1 had no effect on the hsp90-dependent reconstitution of hormone binding to the progesterone receptor in vitro, nor could it substitute for hsp90 to promote maturation of the receptor to its hormone-binding state. However, TRAP1 is sufficiently conserved with hsp90 such that it bound ATP, and this binding was sensitive to the hsp90 inhibitor geldanamycin. In addition, TRAP1 exhibited ATPase activity that was inhibited by both geldanamycin and radicicol. Thus, TRAP1 has functions that are distinct from those of hsp90.
由于通过酵母双杂交筛选克隆出TRAP1和hsp75，分子伴侣的hsp90家族最近得到了扩展。对人类TRAP1和hsp75序列的仔细分析表明它们是相同的，并且我们已经从果蝇中克隆出了一种类似的蛋白质。免疫荧光数据显示人类TRAP1定位于线粒体。人类和果蝇蛋白质氨基末端存在线粒体定位序列支持了这种线粒体定位。由于TRAP1与hsp90具有显著的同源性，我们测试了TRAP1作为类似hsp90的伴侣蛋白发挥功能的能力。TRAP1没有与经典的hsp90共伴侣蛋白p23和Hop（p60）形成稳定的复合物。与这些观察结果一致，TRAP1在体外对hsp90依赖的激素与孕酮受体结合的重建没有影响，它也不能替代hsp90来促进受体成熟到其激素结合状态。然而，TRAP1与hsp90的保守性足以使其结合ATP，并且这种结合对hsp90抑制剂格尔德霉素敏感。此外，TRAP1表现出ATP酶活性，该活性受到格尔德霉素和放线菌酮的抑制。因此，TRAP1具有与hsp90不同的功能。
