Physical map of the zia genes. The ziaA and ziaR genes from Synechocystis PCC 6803, corresponding to ORFs slr0798 and sll0792 in the fully sequenced genome, are shown with an adjacent ORF sll0793, and shaded rectangles coincide with ORFs. ORFs slr0798 and sll0792 have previously been referred to as pacS and pacR, respectively (18), based on similarity of the product of slr0798 to the copper transporter PacS from Synechococcus PCC 7942. The annealing positions of primers used during the generation of plasmid constructs are indicated (vertical lines). An expanded 26-bp region of the zia operator–promoter is marked with arrows to show a degenerate 12-2-12 hyphenated inverted repeat. Nucleotides that are conserved in a similar inverted repeat within the smtA operator–promoter are marked (asterisk) and include guanines (or complement) shown by methylation protection assays to be protected by SmtB (21) (underlined). The site of insertion of a Km resistance gene cassette to disrupt ziaA in Synechocystis PCC 6803 is indicated.