FIG. 4.

Features of the bhuR promoter region. The nucleotide sequence of the bhuR upstream region and 5′ bhuR coding sequences (GenBank accession number AY032627) are shown. Solid vertical lines labeled pRK41, pRK51, pRK50, and pRK45 denote the 5′ limits of the bhuR promoter region used to construct the corresponding bhuR-lacZ plasmid-borne fusions (Table 1). The vertical line labeled 3′ indicates the lacZ fusion junction for all bhuR-lacZ constructs. Nucleotides 343 to 348 and 367 to 372 shown in lowercase letters represent ECF σ-like −35 and −10 elements that were predicted based on similarity to other promoters. The horizontal bar over nucleotides 336 to 347 shows the position of the block substitution mutation constructed in plasmid pRK47; the bar over nucleotides 266 to 271 shows the position of the BglII site engineered in plasmid pRK48. Nucleotide changes are indicated above the bars. Arrows labeled PE1 and PE2 indicate the positions of antisense bhuR primers used in primer extension analyses. The dot denotes the transcription initiation site determined with primer PE2. Amino acids of the N-terminal region of the BhuR protein are designated below the nucleotide sequence.