Global effect of the lack of inorganic polyphosphate in the extremophilic archaeon Sulfolobus solfataricus: A proteomic approach

Abstract

Inorganic polyphosphates (polyP) are present in all living cells and several important functions have been de-scribed for them. They are involved in the response to stress conditions, such as nutrient depletion, oxidativestress and toxic metals amongst others. A recombinant strain ofSulfolobus solfataricusunable to accumulatepolyP was designed by the overexpression of its endogenousppxgene. The overall impact of the lack of polyP onthisS.solfataricuspolyP (−) strain was analyzed by using quantitative proteomics (isotope-coded protein label,ICPL). Stress-related proteins, such as peroxiredoxins and heat shock proteins, proteins involved in metabolismand several others were produced at higher levels in theppxexpression strain. The polyP deficient strain showedan increased copper sensitivity and an earlier transcriptional up-regulation ofcopAgene coding for the P-typecopper-exporting ATPase. This implies a complementary function of both copper resistance systems. These re-sults strongly suggests that the lack of polyP makes this hyperthermophilic archaeon more sensitive to toxicconditions, such as an exposure to metals or other harmful stimuli, emphasizing the importance of this inorganicphosphate polymers in the adaptations to live in the environmental conditions in which thermoacidophilicarchaea thrive.Significance:Inorganic polyphosphate (polyP) are ubiquitous molecules with many functions in living organ-isms. Few studies related to these polymers have been made in archaea. The construction of a polyP deficientrecombinant strain ofSulfolobus solfataricusallowed the study of the global changes in the proteome of thisthermoacidophilic archaeon in the absence of polyP compared with the wild type strain. The results obtainedusing quantitative proteomics suggest an important participation of polyP in the oxidative stress response of thecells and as having a possible metabolic role in the cell, as previously described in bacteria. The polyP deficientstrain also showed an increased copper sensitivity and an earlier transcriptional up-regulation ofcopA, implyinga complementary role of both copper resistance systems.