Fig 2.

DNA sequence and cis-elements for PhoP and GlnR regulation in the upstream region of amtB. The region protected by GlnR from DNase I digestion is underlined and italicized, while the previously bioinformatically deduced GlnR binding sequences is shaded (22). The a sites and b sites within the GlnR-protected region are enlarged and double underlined. The overlined PhoP binding sequences overlapped with the newly identified a3 site and b3 site. The previously deduced three DRus for PhoP binding are boxed and labeled with an “E” for the extension site and a “C” for the core sites (14). P1, represented by bent arrows, indicates the first and major transcription start site for the amtB operon (2). The primer sequences used for DNase I footprinting assay [SCamtBFP(M13F) and SCamtBFP(M13R)] are labeled by arrows.