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.