A mutant of Neurospora crassa deficient in cytochrome c heme lyase activity cannot import cytochrome c into mitochondria.
The nuclear cyt-2-1 mutant of Neurospora crassa is characterized by a gross deficiency of cytochrome c (Bertrand, H., and Collins, R. A. (1978) Mol. Gen. Genet. 166, 1-13). The mutant produces mRNA that can be translated into apocytochrome c in vitro. Apocytochrome c is also synthesized in vivo in cyt-2-1, but it is rapidly degraded and thus does not accumulate in the cytosol. Mitochondria from wild-type cells bind apocytochrome c made in vitro from either wild-type or cyt-2-1 mRNA and convert it to holocytochrome c. This conversion depends on the addition of heme by cytochrome c heme lyase and is coupled to translocation of cytochrome c into the intermembrane space. Mitochondria from the cyt-2-1 strain are deficient in the ability to bind apocytochrome c. They are also completely devoid of cytochrome c heme lyase activity. These defects explain the inability of the cyt-2-1 mutant to convert apocytochrome c to the holo form and to import it into mitochondria.
Nargang
F E
FE
Department of Genetics, University of Alberta, Edmonton, Canada.
Drygas
M E
ME
Kwong
P L
PL
Nicholson
D W
DW
Neupert
W
W
D002872:Chromosome Deletion; D003574:Cytochrome c Group / Q000378:metabolism*; D005796:Genes; D005800:Genes, Fungal; D008190:Lyases / Q000235:genetics*; D008928:Mitochondria / Q000378:metabolism*; D009154:Mutation; D009491:Neurospora / Q000235:genetics*; D009492:Neurospora crassa / Q000235:genetics* / Q000378:metabolism; D011061:Poly A / Q000235:genetics / Q000302:isolation & purification; D014176:Protein Biosynthesis; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger
D003574:Cytochrome c Group; D012333:RNA, Messenger; D011061:Poly A; D012313:RNA; D008190:Lyases; C031581:cytochrome C synthetase