Pratje E, Guiard B
EMBO J. 1986 Jun;5(6):1313-7. doi: 10.1002/j.1460-2075.1986.tb04361.x.
The proteolytic processing of the mitochondrially encoded subunit II of cytochrome oxidase is prevented by the yeast mutation ts2858. We report that the mutant is, in addition, temperature sensitive for the processing of cytochrome b2, a protein encoded by nuclear DNA. Thus the same mutation affects the removal of pre-sequences from a mitochondrially encoded inner membrane protein and from an imported soluble protein located in the intermembrane space. The mutation blocks the second processing step of cytochrome b2. The cytochrome b2 intermediate accumulates in the mutant at 36 degrees C and assumes its enzyme activity. At 23 degrees C the conversion to the mature protein is considerably slower than in wild-type cells. The similarity of the cleavage sites Asn-Asp and Asn-Glu of the precursors for cytochrome oxidase subunit II and cytochrome b2, respectively, suggests a sequence-specific recognition by one protease or a factor activating a protease. On the other hand maturation of cytochrome c peroxidase, another enzyme of the intermembrane space, is not affected by the pet ts2858 mutation.
酵母突变体ts2858可阻止细胞色素氧化酶线粒体编码亚基II的蛋白水解加工。我们报告称，该突变体对细胞色素b2（一种由核DNA编码的蛋白质）的加工同样具有温度敏感性。因此，同一突变影响了从线粒体编码的内膜蛋白以及位于膜间隙的导入可溶性蛋白中去除前导序列。该突变阻断了细胞色素b2的第二步加工。细胞色素b2中间体在36℃时在突变体中积累并具有酶活性。在23℃时，向成熟蛋白的转化比野生型细胞中要慢得多。细胞色素氧化酶亚基II和细胞色素b2前体的切割位点分别为天冬酰胺-天冬氨酸和天冬酰胺-谷氨酸，这一相似性表明可能存在一种蛋白酶或激活蛋白酶的因子对序列进行特异性识别。另一方面，膜间隙的另一种酶——细胞色素c过氧化物酶的成熟不受pet ts2858突变的影响。
