The HiPIP from the acidophilic Acidithiobacillus ferrooxidans is correctly processed and translocated in Escherichia coli, in spite of the periplasm pH difference between these two micro-organisms

Abstract

The gene encoding a putative high-potential iron–sulfur protein (HiPIP) from the strictly acidophilic and chemolithoautotrophicAcidithiobacillus ferrooxidansATCC 33020 has been cloned and sequenced. This potential HiPIP was overproduced in the periplasm of the neutrophile and heterotrophEscherichia coli. As shown by optical and EPR spectra and by electrochemical studies, the recombinant protein has all the biochemical properties of a HiPIP, indicating that the iron–sulfur cluster was correctly inserted. Translocation of this protein in the periplasm ofE. coliwas not detected in a ΔtatCmutant, indicating that it is dependent on the Tat system. The genetic organization of theirolocus in strains ATCC 23270 and ATCC 33020 is different from that found in strains Fe-1 and BRGM. Indeed, inA. ferrooxidansATCC 33020 and ATCC 23270 (the type strain),irowas not located downstream frompurAbut was instead downstream frompetC2, encoding cytochromec1from the secondA. ferrooxidanscytochromebc1complex. These findings underline the genotypic heterogeneity within theA. ferrooxidansspecies. The results suggest that Iro transfers electrons from a cytochromebc1complex to a terminal oxidase, as proposed for the HiPIP in photosynthetic bacteria.