Molecular cloning and sequencing of the ferredoxin I fdxN gene of the photosynthetic bacterium Rhodospirillum rubrum.

Using an oligonucleotide probe derived from the amino acid sequence of Rhodospirillum rubrum ferredoxin I, the gene (fdxN) was identified, cloned and sequenced. The FdxN coding region is 183 nucleotides which codes for a 61 amino acid (7267 Da) protein. Phylogenetic comparisons between the R. rubrum FdI and other 8Fe-8S nif-coupled ferredoxins showed only moderate degrees of similarity between the amino acid sequences. R. rubrum FdI synthesis was stimulated by nif derepressing conditions, but was not completely repressed by nif repression. Previous reports of an extracellular clostridial-type ferredoxin in R. rubrum could not be confirmed.