FIG. 2.

Promoter region of nifHDK. (A) Sequence of the genomic region upstream of nifH and of the fusion of the promoter region of nifH fused to fdxN in plasmid pfdxN. The arrow indicates the putative transcription start site, and the unlabeled box indicates the possible start codon. Regulatory sequences are boxed and labeled: UAS, putative upstream activating sequence; −12/−24 region, putative ς⁵⁴-dependent promoter region; RBS, putative Shine-Dalgarno sequence of nifH. The putative RBS of the other genes of the nifHDK region are given at the bottom, as well as the sequence of the fusion region in plasmid pfdxN. (B) Primer extension analysis localizing the transcriptional start at minute 158.6, corresponding to nucleotides 541/542 (159 and 158.2 min). Top, sequencing reaction; bottom, primer extension.