Blackwell Publishing Journal Backfiles 1879-2005
Nucleotide sequences of nifHD from Frankia strain EuIKl were determined and analysed. The 3.2-kb and 5.5-kb BamHI fragments of a genomic clone were previously shown to contain nifHD-like sequences and to be contiguous, based on hybridization experiments and partial sequencing data. Sequence analysis of about 3.0 kb from these fragments revealed two open reading frames and beginning of a third in the same orientation, each of which showed high degree of sequence homology with nifH, nifD and nifK, respectively. The deduced amino acid sequence of the nifH ORF, consisting of 861 bp, showed sequence similarity of about 91% with those of other Frankia strains, whereas that of nifD ORF, consisting of 1458 bp, showed about 85% similarity. Intergenic sequence between nifH and nifD was 45 bp and between nifD and nifK was 61 bp. The 5’of nifH revealed putative Shine-Dalgarno sequences; however, a sequence resembling a typical nif-promoter or NifA binding site was not found. Northern hybridization of RNA from the nodules showed that nifHDK were transcribed into a polycistronic mRNA in the symbiont of Elaeagnus umbellata.
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