Pearce D A, Sherman F
Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA.
Arch Biochem Biophys. 1998 Apr 1;352(1):85-96. doi: 10.1006/abbi.1998.0591.
Altered iso-1- and iso-2-cytochromes c, with certain amino acid replacements, occur at diminished levels due to degradation in the yeast Saccharomyces cerevisiae. A subclass of the labile isocytochromes c are significantly protected from degradation by the presence of cytochromes a.a3 and c1, the physiological partners of cytochrome c. We have investigated the degradation that is dependent on physiological partners by examining the levels of iso-1-cytochrome c having all or most amino acid replacements at positions 6, 41, 52, and 78, in both rho+ strains and rho- strains, which lacks cytochrome a.a3. In addition, we have examined some of these replacements in strains also having the N52I replacement, which suppresses a variety of abnormal iso-1-cytochromes c, including those whose degradation is either dependent or independent on the physiological partners. Although some degree of preferential rho--dependent reductions was observed for iso-1-cytochromes c having replacements at each of the 6, 41, 52, and 78 sites, prominent effects of rho+/rho- ratios of approximately 100/0 to 30/0 were observed for iso-1-cytochromes c having replacements mainly at the 41, 52, and 78 sites, but not the G6 site. We suggest that prominent degradation dependent on physiological partners may be restricted to certain regions of the cytochrome c molecule. Furthermore, we suggest that the region of the largest confirmational difference between oxidized and reduced cytochrome c appears to be particularly protected by interactions with its physiological partners.
在酿酒酵母中，由于降解作用，具有特定氨基酸替换的异 - 1 - 细胞色素c和异 - 2 - 细胞色素c水平降低。一类不稳定的异细胞色素c由于细胞色素c的生理伴侣细胞色素a.a3和c1的存在而受到显著的降解保护。我们通过检测rho +菌株和缺乏细胞色素a.a3的rho - 菌株中，在第6、41、52和78位具有全部或大部分氨基酸替换的异 - 1 - 细胞色素c的水平，研究了依赖生理伴侣的降解情况。此外，我们还检测了在同时具有N52I替换的菌株中的一些此类替换情况，N52I替换可抑制多种异常的异 - 1 - 细胞色素c，包括那些降解依赖或不依赖生理伴侣的异 - 1 - 细胞色素c。尽管在第6、41、52和78位具有替换的异 - 1 - 细胞色素c观察到一定程度的rho - 依赖性优先降低，但对于主要在第41、52和78位而非G6位具有替换的异 - 1 - 细胞色素c，观察到rho + / rho - 比率约为100/0至30/0时的显著影响。我们认为，依赖生理伴侣的显著降解可能局限于细胞色素c分子的某些区域。此外，我们认为氧化型和还原型细胞色素c之间构象差异最大的区域似乎通过与其生理伴侣的相互作用而受到特别保护。
