SurR: a transcriptional activator and repressor controlling hydrogen and elemental sulphur metabolism in Pyrococcus furiosus

This work describes the identification and characterization of SurR, Pyrococcus furiosus sulphur (S⁰) response regulator. SurR was captured from cell extract using promoter DNA of a hydrogenase operon that is downregulated in the primary response of P. furiosus to S⁰, as revealed by DNA microarray experiments. SurR was validated as a sequence-specific DNA binding protein, and characterization of the SurR DNA binding motif GTTn₃AAC led to the identification of several target genes that contain an extended motif in their promoters. A number of these were validated to contain upstream SurR binding sites. These SurR targets strongly correspond with open reading frames and operons both up- and downregulated in the primary response to S⁰. In vitro transcription revealed that SurR is an activator for its own gene as well as for two hydrogenase operons whose expression is downregulated during the primary S⁰ response; it is also a repressor for two genes upregulated during the primary S⁰ response, one of which encodes the primary S⁰-reducing enzyme NAD(P)H sulphur reductase. Herein we give evidence for the role of SurR in both mediating the primary response to S⁰ and controlling hydrogen production in P. furiosus.