A mutant of Neurospora crassa deficient in cytochrome c heme lyase activity cannot import cytochrome c into mitochondria.

Nargang, Frank E.; Drygas, Mariola E.; Kwong, Patrick; Nicholson, Donald W.; Neupert, Walter

doi:10.1016/s0021-9258(19)76553-3

Cited by 94 publications

(5 citation statements)

References 35 publications

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“…In the IMS, the heme group is incorporated into apocytochrome c in a reaction catalyzed by cytochrome c heme lyase, a component located on the IMS side of the inner membrane. In the absence of cytochrome c heme lyase, cytochrome c fails to be imported, suggesting that cofactor acquisition is a prerequisite for net translocation across the outer membrane (Nargang et al ., 1988; Dumont et al ., 1991).…”

Section: Introductionmentioning

confidence: 99%

Import of small Tim proteins into the mitochondrial intermembrane space

2003

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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.

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Section: Introductionmentioning

confidence: 99%

Import of small Tim proteins into the mitochondrial intermembrane space

2003

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“…A further possibility is that binding of apocytochrome c to another component, prior to the interaction with the heme lyase, is also required in the soluble system. To further support the first hypothesis, it has been observed that a Neurospora crassa mutant which lacks CCHL activity is not only deficient in cytochrome c import, but also in the specific binding of apocytochrome c (Nargang et al, 1988).…”

Section: Import Of Cytochrome Cmentioning

confidence: 96%

“…The availability of this mutant, and of a similar one in yeast, has allowed the cloning and the determination of the primary structure of CCHL from both organisms (Dumont et al, 1987;Drygas et al, 1989, Nargang et al, 1988. The proteins show 32% homology (49% if conservative substitutions of amino acid residues are included), with the most conserved regions clustered in the C-terminal half of the polypeptide.…”

Section: Import Of Cytochrome Cmentioning

confidence: 99%

Biogenesis of mitochondrialc-type cytochromes

Gonzales

Neupert

1990

J Bioenerg Biomembr

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Cytochromes e and c I are essential components of the mitochondrial respiratory chain. In both cytochromes the heme group is covalently linked to the polypeptide chain via thioether bridges. The location of the two cytochromes is in the intermembrane space; cytochrome c is loosely attached to the surface of the inner mitochondrial membrane, whereas cytochrome c~ is firmly anchored to the inner membrane. Both cytochrome c and c~ are encoded by nuclear genes, translated on cytoplasmic ribosomes, and are transported into the mitochondria where they become covalently modified and assembled. Despite the many similarities, the import pathways of cytochrome c and c 1 are drastically different. Cytochrome c I is made as a precursor with a complex bipartite presequence. In a first step the precursor is directed across outer and inner membranes to the matrix compartment of the mitochondria where cleavage of the first part of the presequence takes place. In a following step the intermediate-size form is redirected across the inner membrane; heme addition then occurs on the surface of the inner membrane followed by the second processing reaction. The import pathway of cytochrome c is exceptional in practically all aspects, in comparison with the general import pathway into mitochondria. Cytochrome c is synthesized as apocytochrome c without any additional sequence. It is translocated selectively across the outer membrane. Addition of the heine group, catalyzed by cytochrome c heme lyase, is a requirement for transport. In summary, cytochrome c I import appears to follow a "conservative pathway" reflecting features of cytochrome c~ sorting in prokaryotic cells. In contrast, cytochrome c has "invented" a rather unique pathway which is essentially "non-conservative."

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“…Another example of this folding trap mechanism is the retention of cytochrome c (Cyc1) in the IMS, which requires binding to cytochrome c heme lyase (Cyc3/CCHL). Cyc3 is found in the IMS associated with the inner membrane [76], and catalyses the attachment of a heme group to Cyc1. The superoxide dismutase, Sod1, is another metal-binding protein that is imported via a folding trap [77].…”

Section: Thou Shalt Not Pass: No Escape From the Folding Trapmentioning

confidence: 99%