Cloning and characterization of thermostable GroEL/GroES homologues from Geobacillus thermopakistaniensis and their applications in protein folding

The chaperonin genes encoding GroELGt (ESU72018) and GroESGt (ESU72017), homologues of bacterial GroEL and GroES, from Geobacillus thermopakistaniensis were cloned and expressed in Escherichia coli. The purified gene products possessed the ATPase activity similar to other bacterial and eukaryal counterparts. Recombinant GroELGt and GroESGt were able to refold the denatured insoluble aggregates of α-amylase from Bacillus licheniformis into soluble and active form. Furthermore, GroELGt and GroESGt successfully enhanced the thermostability of porcine heart malate dehydrogenase. Expression of GroELGt gene in E. coli cells enhanced the thermotolerance of the host. Furthermore, soluble production of recombinant alcohol dehydrogenase from Bacillus subtilis strain R5 in E. coli, initially produced as insoluble aggregates, was achieved by co-expressing the gene with GroELGt. Our results implied that GroELGt could assist folding of nascent protein in E. coli with the help of host co-chaperonin without requiring additional ATP. This system can be used for soluble production of recombinant proteins which otherwise are produced in insoluble form in E. coli. To the best of our knowledge this is the first report on functional characterization and applications of chaperonins from genus Geobacillus.