Abstract

Background and Objective: CsaA is a molecular chaperone known to prevent aggregation of preproteins and also involved in the post-translational translocation of the proteins across the cytoplasmic membrane after correct folding. CsaA is known to be present in prokaryotes but is absent in eukaryotes. Although bacterial CsaA has been studied to some extent, there are no reports yet of crystallographic studies of CsaA from any of the archaeal organisms.

Method: In the present investigation, we report for the first time the cloning, expression, purification and crystallographic diffraction data collection on CsaA from Picrophilus torridus (PtCsaA), which is a thermoacidophilic archaeon. PtCsaA was cloned in pET28a(+) and expressed in E. coli BL21(DE3), purified using metal affinity and gel filtration chromatography.

Results and Conclusion: Crystallization trials with purified PtCsaA protein resulted in crystals suitable for Xray diffraction analysis. The crystals belonged to the orthorhombic space group P212121 and diffracted to the resolution limit of about 1.70 Å. Structure solution is expected to proceed using molecular replacement methods. The comparison of the resulting model structure to its counterparts from bacteria is expected to throw light on the structural similarities and differences between the homologs found in the two prokaryotic domains.

Keywords: Chaperones, archaea, Picrophilus torridus, cloning, crystallization, X-ray diffraction.

Graphical Abstract