Among lignocellulolytic enzymes, laccases are the most versatile, broadly specific, and largely studied enzyme with a wide range of biotechnological potential. Putative laccase (CotA) from Bacillus pumilus MK001 was cloned and expressed in E. coli. In addition to soluble bioactive fraction, inactive inclusion body fraction was also harvested and refolded under optimized conditions resulting in 64 % of refolding efficiency. The enzyme was found to be thermostable exhibiting a half-life of 60 min at 80 °C. UV thermal CD spectra also supported the observation as about 9 % increase in β-sheets was recorded after thermal induction. The 3D CotA structure was constructed through homology modeling and the best selected model was verified through PROCHECK, ERRAT, Verify 3D, and PROSA servers. Final 3D model showed potential binding affinities with ferulic acid, caffeic acid, and vanillin. Results of the docking studies were further validated by HPLC analysis which signified the efficient bioconversion ability of CotA.

No abstract

No abstract

CsaA is a protein involved in the post-translational translocation of proteins across the cytoplasmic membrane. It is considered to be a functional homolog of SecB which participates in the Sec-dependent translocation pathway in an analogous manner. CsaA has also been reported to act as a molecular chaperone, preventing aggregation of unfolded proteins. It is essentially a prokaryotic protein which is absent in eukaryotes, but found extensively in bacteria and earlier thought to be widely present in archaea. The study of phylogenetic distribution of CsaA among prokaryotes suggests that it is present only in few archaeal organisms, mainly species of Thermoplasmatales and Halobacteriales. Interestingly, the CsaA protein from these two archaeal orders cluster separately on the phylogenetic tree with CsaA from Gram-positive and Gram-negative bacteria. It, thus, appears that this protein might have been acquired in these archaeal organisms through independent horizontal gene transfer (HGT) events from different bacteria. In this review, we summarize the earlier biochemical, structural, and functional characterization studies of CsaA. We draw new insights into the evolutionary history of this protein through phylogenetic and structural comparison of bacterial CsaA with modelled archaeal CsaA from Picrophilus torridus and Natrialba magadii.

Molecular chaperones are a diverse group of proteins that ensure proteome integrity by helping the proteins fold correctly and maintain their native state, thus preventing their misfolding and subsequent aggregation. The chaperone machinery of archaeal organisms has been thought to closely resemble that found in humans, at least in terms of constituent players. Very few studies have been ventured into system-level analysis of chaperones and their functioning in archaeal cells. In this study, we attempted such an analysis of chaperone-assisted protein folding in archaeal organisms through network approach using Picrophilus torridus as model system. The study revealed that DnaK protein of Hsp70 system acts as hub in protein-protein interaction network. However, DnaK protein was present only in a subset of archaeal organisms and absent from many archaea, especially members of Crenarchaeota phylum. Therefore, a similar network was created for another archaeal organism, Sulfolobus solfataricus, a member of Crenarchaeota. The chaperone network of S. solfataricus suggested that thermosomes played an integral part of hub proteins in archaeal organisms, where DnaK was absent. We further compared the chaperone network of archaea with that found in eukaryotic systems, by creating a similar network for Homo sapiens. In the human chaperone network, the UBC protein, a part of ubiquitination system, was the most important module, and interestingly, this system is known to be absent in archaeal organisms. Comprehensive comparison of these networks leads to several interesting conclusions regarding similarities and differences within archaeal chaperone machinery in comparison to humans.