Identification of Binding Partners of CsaA - An Archaeal Chaperonic Protein of Picrophilus torridus.

Abstract

CsaA is among the few chaperones which are present in both bacteria and archaea, but absent in eukaryotes. There are no reports on interactome analysis of CsaA from archaea, till date. Identification of binding partners of CsaA might be helpful in understanding CsaA-associated processes in Picrophilus torridus an extreme thermoacidophilic euryarchaeon. The present study was conducted to identify the binding partners of CsaA of P. torridus (PtCsaA). The binding partners of PtCsaA were isolated and identified using a pull down assay and liquid chromatography-mass spectrometry (LC-MS). The results revealed twelve potential binding partners of CsaA. These were thermosome subunits (Q6KZS2 and Q6L132), nascent polypeptide-associated complex protein (Q6L1N3), elongation factor 1-alpha (Q6L202), uncharacterized protein (Q6L0Y6), citrate synthase (Q6L0M8), asparaginyl- tRNA synthetase (Q6L0M5), succinyl-CoA synthetase beta chain (Q6L0B4), pyruvate ferredoxin oxidoreductase alpha and beta chain proteins (Q6KZA7 and Q6KZA6, respectively), malate dehydrogenase (Q6L0C3) and reversed fumarylacetoacetase (Q6KZ97). Functional categorization revealed that of these, six proteins were involved in energy metabolic pathways, three were archaeal chaperones, two were involved in translation and one might be a transcription regulator. STRING-based analysis of the protein-protein interactions of the experimental interactome revealed strong interactions among them. PtCsaA might be a multifaceted protein which besides translation might also play important role in metabolic processes of P. torridus. However, further experiments investigating the binding partners of CsaA in other archaea are required for a better understanding of CsaA-associated processes in archaea.