Stuart R A, Nicholson D W, Wienhues U, Neupert W
Institut für Physiologische Chemie, Universität München, Federal Republic of Germany.
J Biol Chem. 1990 Nov 25;265(33):20210-9.
The question of whether cytochrome c could be functionally sorted to the mitochondrial intermembrane space along a "conservative sorting" pathway was investigated using a fusion protein termed pLc1-c. pLc1-c contains 3-fold targeting information, namely, the complete bipartite presequence of the cytochrome c1 precursor joined to the amino terminus of apocytochrome c. pLc1-c could be selectively imported into the intermembrane space either directly across the outer membrane along a cytochrome c import route or along a cytochrome c1 route via the matrix. Thus, apocytochrome c could be sorted along a conservative sorting pathway; however, following reexport from the matrix, apo-Lc1-c could not be converted to its holo counterpart. Despite the apparent similarity of structure and functional location of the heme lyases and similarity of the heme binding regions in their respective apoproteins, cytochrome c heme lyase and cytochrome c1 heme lyase apparently have different and nonoverlapping substrate specificities.
利用一种名为pLc1-c的融合蛋白，研究了细胞色素c是否能沿着“保守分选”途径在功能上被分选到线粒体外膜间隙的问题。pLc1-c包含三重靶向信息，即细胞色素c1前体的完整双组分前导序列连接到脱辅基细胞色素c的氨基末端。pLc1-c可以沿着细胞色素c导入途径直接穿过外膜，或者通过基质沿着细胞色素c1途径选择性地导入到外膜间隙。因此，脱辅基细胞色素c可以沿着保守分选途径进行分选；然而，从基质中再输出后，脱辅基-Lc1-c不能转化为其全酶形式。尽管血红素裂解酶的结构和功能位置明显相似，且它们各自脱辅基蛋白中的血红素结合区域也相似，但细胞色素c血红素裂解酶和细胞色素c1血红素裂解酶显然具有不同且不重叠的底物特异性。
