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Structural and Functional Analyses of the Genes for Subunit II of Cytochrome aa3 and for a Dicyclohexylcarbodiimide-binding Protein in Neurospora crassa Mitochondrial DNA

Paul van den Boogaart, John Samallo, Simon van Dijk, Etienne Agsteribbe


The use of well-defined fragments of yeast mitochondrial genes as probes in hybridization has made it possible to localize protein genes in Neurospora crassa mtDNA (Agsteribbe et al. 1980; Macino 1980). In addition to the positions of the genes for subunits I, II, and III of cytochrome aa3, for cytochrome b, and for the 19,000-dalton subunit of mitochondrial ATPase, we have discovered a sequence homologous to the gene for the yeast mitochondrial dicyclohexylcarbodiimide (DCCD)-binding protein, also referred to as the ATPase proteolipid. This sequence was found in close proximity to the gene for subunit II of cytochrome aa3. The presence in Neurospora mtDNA of the former sequence is intriguing, since it has been demonstrated that in Neurospora the ATPase proteolipid is coded by a nuclear gene (Sebald et al. 1979). To establish whether the Neurospora mitochondrial sequence is a nonfunctional gene for an ATPase proteolipid or whether it codes for a related protein and to verify the presence of the gene for subunit II of cytochrome aa3, we have determined their respective base sequences and have investigated transcription from this region.

The gene for subunit II of cytochrome aa3 and the sequence homologous to the yeast mitochondrial gene for the ATPase proteolipid are located in EcoRI fragment 4 of Neurospora mtDNA. As a first step toward base sequence analysis and transcription mapping, we have constructed a map of this fragment (Fig. 1).

Base sequence analysis of part of the Neurospora subunit-II gene showed an overall homology of...

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