Expression of an archaeal chaperonin in E. coli: formation of homo‐ (α, β) and hetero‐oligomeric (α + β) thermosome complexes

Co-expression of the two genes encoding the alpha- and beta-subunit of the Thermoplasma acidophilum thermosome in Escherichia coli yielded fully assembled hetero-oligomeric complexes (alpha+beta). Surprisingly, also separate expression of both genes resulted in formation of hexadecameric complexes (alpha, beta) in the bacterial cytoplasm. On electron micrographs these complexes were indistinguishable from each other and from the native thermosome. The recombinant alpha-complex as well as the native thermosome could be reconstituted in vitro from their dissociated subunits in the presence of Mg-ATP.