The elemental sulfur-responsive protein (SipA) from the hyperthermophilic archaeon Pyrococcus furiosus is regulated by sulfide in an iron-dependent manner

Abstract

The gene (sipA) encoding the sulfur-induced protein A (PF2025) is highly upregulated during growth of Pyrococcus furiosus on elemental sulfur (S(0)). Expression of sipA is regulated by sulfide, the product of S(0) reduction, but in an iron-dependent manner. SipA is proposed to play a role in intracellular iron sulfide detoxification.

FIG. 1.

RNA levels change with added sulfide and iron. QPCR results for sipA (a) and nsr (b) from P. furiosus grown with sulfide (5, 10, or 20 mM) or 1 g/liter S⁰, with or without 7.4 μM iron present. Results are compared to base media with no sulfide or S⁰ added. Data are from three separate growths and are graphed as log₂-fold change values with error bars indicating standard deviations. Corresponding fold change values for significant regulation are labeled.

FIG. 2.

SipA protein levels change with added sulfide and iron. (a) Western blot analysis of SipA in whole-cell extract from P. furiosus grown in at least two independent cultures with added sulfide or S⁰. The constitutively expressed protein SOR was used as a loading control. Lane 1, 1 g/liter of S⁰; lanes 2 to 4, no S⁰ or sulfide; lanes 5 to 6, 5 mM sulfide; lanes 7 to 8, 10 mM sulfide; lanes 9 to 10, 20 mM sulfide. (b) Western blot analysis of SipA in whole-cell extract of P. furiosus from cultures grown with and without 1 g/liter of S⁰ and with and without 7.4 μM iron added.