Interactions among COX1, COX2, and COX3 mRNA-specific translational activator proteins on the inner surface of the mitochondrial inner membrane of Saccharomyces cerevisiae.
The core of the cytochrome c oxidase complex is composed of its three largest subunits, Cox1p, Cox2p, and Cox3p, which are encoded in mitochondrial DNA of Saccharomyces cerevisiae and inserted into the inner membrane from the inside. Mitochondrial translation of the COX1, COX2, and COX3 mRNAs is activated mRNA specifically by the nuclearly coded proteins Pet309p, Pet111p, and the concerted action of Pet54p, Pet122p, and Pet494p, respectively. Because the translational activators recognize sites in the 5'-untranslated leaders of these mRNAs and because untranslated mRNA sequences contain information for targeting their protein products, the activators are likely to play a role in localizing translation. Herein, we report physical associations among the mRNA-specific translational activator proteins, located on the matrix side of the inner membrane. These interactions, detected by coimmune precipitation and by two-hybrid experiments, suggest that the translational activator proteins could be organized on the surface of the inner membrane such that synthesis of Cox1p, Cox2p, and Cox3p would be colocalized in a way that facilitates assembly of the core of the cytochrome c oxidase complex. In addition, we found interactions between Nam1p/Mtf2p and the translational activators, suggesting an organized delivery of mitochondrial mRNAs to the translation system.
Naithani
Sushma
S
Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853-2703, USA.
Saracco
Scott A
SA
Butler
Christine A
CA
Fox
Thomas D
TD
D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D007527:Isoenzymes / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D008928:Mitochondria / Q000201:enzymology* / Q000378:metabolism; D024101:Mitochondrial Proteins; D009687:Nuclear Proteins / Q000378:metabolism; D010448:Peptide Initiation Factors; D011233:Precipitin Tests; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors / Q000378:metabolism; D020798:Two-Hybrid System Techniques
D007527:Isoenzymes; C063626:MTF2 protein, S cerevisiae; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D009687:Nuclear Proteins; C087048:PET111 protein, S cerevisiae; C095480:PET309 protein, S cerevisiae; D010448:Peptide Initiation Factors; D012333:RNA, Messenger; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; C466421:cyclooxygenase-3