The Localization Of Mrzl Protein In Schizosaccharomyces Pombe And Its Effect On Mitochondrial Protein Translation

Mitochondria are eukaryotic organelles involved in many cellular functions including adenosine triphosphate(ATP)production through oxidative phosphorylation(OXPHOS),amino acid and fatty acid synthesis,apoptosis and the aging process in animals.The fission yeast Schizosaccharomyces pombe is an attractive model system for understanding mitochondrial gene expression.The mitochondrial genome(mtDNA)of the fission yeast S.pombe is a compact,linear DNA of-19 kb.It encodes key subunits of the OXPHOS complexes,such as cytochrome b-cl complex(complex III)subunit 3(Cob1,also called Cob or Cytb),cytochrome c oxidase(complex IV or COX)subunits 1,2,3(Cox1,2,3)and ATP synthase(complex V)subunits(Atp6,8,9).In addition,S.pombe mtDNA encodes mitochondrial ribosomal protein(Varl),the large and small subunits of the mitochondrial ribosome(rnl and rns),25tRNAs and the RNA subunit of RNase P(rnpB).Mrzl protein is a functional unknown protein,in this study,we focuse on studing the localization and funcation of a fission yeast Schizosaccharomyces pombe protein,Mrzl.By constructing Amrzl strain,we found that mrzl deletion mutant exhibits growth well in enriched medium while growth defects in respiratory media,it suggests that Mrzl is closely related to mitochondrial function.It was found that Mrzl protein was a mitochondrial outer membrane protein through the localization experiment was conducted by extracting the mitochondria.By quantitative real-time RT-PCR,deletion of mrzl does not affect the accumulation of specific mitochondrial mRNAs.Furthermore,the effects of deletion of mrzl on the level of mitochondrial protein were detected through[35S]-methionine/cysteine mix markers and Western blot.We found that deletion of mrzl does not affect the synthesis of mitochondrial protein,but severely impairs the stability of the mitochondrial protein Cob1,Cox1,Cox2 and Cox3,suggesting that Mrzl plays a general role in mitochondrial protein stability.Deletion of mrzl results in mitochondrial protein unstable and then degraded,which affect the mitochondrial respiratory chain complex assembly and the mitochondrial oxidative phosphorylation,thus mitochondrial function is impaired.