Import of small Tim proteins into the mitochondrial intermembrane space

被引:94
作者
Lutz, T [1 ]
Neupert, W [1 ]
Herrmann, JM [1 ]
机构
[1] Univ Munich, Inst Physiol, D-81377 Munich, Germany
关键词
folding; intermembrane space; mitochondria; protein translocation; Tim13; INNER MEMBRANE-PROTEINS; C HEME LYASE; SACCHAROMYCES-CEREVISIAE; YEAST MITOCHONDRIA; CYTOCHROME-C; TRANSLOCATION; COMPLEX; PATHWAYS; SIGNALS; SHUTTLE;
D O I
10.1093/emboj/cdg421
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Proteins of the intermembrane space (IMS) of mitochondria are typically synthesized without presequences. Little is known about their topogenesis. We used Tim13, a member of the 'small Tim protein' family, as model protein to investigate the mechanism of translocation into the IMS. Tim13 contains four conserved cysteine residues that bind a zinc ion as cofactor. Import of Tim13 did not depend on the membrane potential or ATP hydrolysis. Upon import into mitochondria Tim13 adopted a stably folded conformation in the IMS. Mutagenesis of the cysteine residues or pretreatment with metal chelators interfered with folding of Tim13 in vitro and impaired its import into mitochondria. Upon depletion of metal ions or modification of cysteine residues, imported Tim13 diffused back out of the IMS. We propose an import pathway in which (1) Tim13 can pass through the TOM complex into and out of the IMS in an unfolded conformation, and (2) cofactor acquisition stabilizes folding on the trans side of the outer membrane and traps Tim13 in the IMS, and drives unidirectional movement of the protein across the outer membrane of mitochondria.
引用
收藏
页码:4400 / 4408
页数:9
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