PRIMARY STRUCTURE OF A FERREDOXIN-LIKE IRON-SULFUR SUBUNIT OF COMPLEX-I FROM NEUROSPORA-CRASSA

We have isolated cDNA clones encoding an iron-sulfur polypeptide subun it of the mitochondrial complex I of Neurospora crassa. The fungal cDN A library was screened by hybridisation with an heterologous probe fro m Paracoccus denitrificans. The DNA sequence of relevant isolates was determined and revealed an open reading frame encoding a precursor pro tein of 219 amino acid residues. The gene product is a ferredoxin-like protein that contains two cysteine-rich motives that may each bind a tetranuclear iron-sulfur cluster. The primary structure of the protein is highly homologous to the 23 kDa iron-sulfur subunit of complex I f rom bovine and P. denitrificans. Interestingly, an alanine residue wit hin the second cluster-binding motif, which is conserved in complex I but replaced by tyrosine in similar chloroplast genes, is substituted for serine in N. crassa.