Sheluho D, Ackerman S H
Department of Surgery, Wayne State University School of Medicine, 1225 Ellman Bldg., 421 E. Canfield Ave., Detroit, MI 48201, USA.
J Biol Chem. 2001 Oct 26;276(43):39945-9. doi: 10.1074/jbc.M107252200. Epub 2001 Aug 24.
Atp11p is a soluble protein of mitochondria that binds unassembled beta subunits of the F(1)-ATPase and prevents them from aggregating in the matrix. In this report, we show that Atp11p protects the insulin B chain from aggregating in vitro and therefore acts as a molecular chaperone. The chaperone action of Atp11p is mediated by hydrophobic interactions. An accessible hydrophobic surface in Atp11p was identified with the environment-sensitive fluorescent probe 1,1'-bis(4-anilino-5-napththalenesulfonic acid (bis-ANS). The spectral changes of bis-ANS in the presence of Atp11p indicate that the probe binds to a nonpolar region of the protein. Furthermore, the dye quenches the fluorescence of Atp11p tryptophan residues in a concentration-dependent manner. Although up to three molecules of bis-ANS can bind cooperatively to Atp11p, the binding of only one dye molecule is sufficient to virtually eliminate the chaperone activity of the protein.
Atp11p是一种线粒体可溶性蛋白，它能结合F(1)-ATP酶未组装的β亚基，防止它们在基质中聚集。在本报告中，我们表明Atp11p在体外可保护胰岛素B链不发生聚集，因此起到分子伴侣的作用。Atp11p的伴侣作用是由疏水相互作用介导的。利用环境敏感荧光探针1,1'-双(4-苯胺基-5-萘磺酸)(bis-ANS)确定了Atp11p中一个可及的疏水表面。bis-ANS在Atp11p存在时的光谱变化表明该探针与蛋白质的一个非极性区域结合。此外，该染料以浓度依赖的方式淬灭Atp11p色氨酸残基的荧光。虽然多达三个bis-ANS分子可以协同结合到Atp11p上，但仅一个染料分子的结合就足以几乎消除该蛋白质的伴侣活性。
