A mitochondrial reading frame which may code for a second form of ATPase subunit 9 in Aspergillus nidulans

Summary The nucleotide sequence of a 74 codon reading frame from the Aspergillus nidulans mitochondrial genome is presented. The derived amino acid sequence displays typical features of dicyclohexylcarbodiimide (DCCD) binding proteins and is 84% homologous with a mitochondrial reading frame that potentially encodes an ATPase subunit 9 polypeptide in Neurospora crassa. However, in A. nidulans, as in N. crassa, there is strong biochemical and genetic evidence that this subunit is in fact nuclearly-encoded. In both organisms the DCCD-binding protein found in the F₀ complexes of mitochondria from actively-growing cultures is almost certainly the product of this nuclear gene, and definitely not that of the mitochondrial reading frame. The discovery of an intact open reading frame than can code for a DCCD-binding protein in the mitochondrial genome of a second species of filamentous fungus strenghthens the possibility that the presence of a mitochondrial version of this gene has some biological significance.