We report the characterization of the first chaperonin (Mm-cpn) from a mesophilic archaeon, Methanococcus maripaludis. The single gene was cloned from genomic DNA and expressed in Escherichia coli to produce a recombinant protein of 543 amino acids. In contrast with other known archaeal chaperonins, Mm-cpn is fully functional in all respects under physiological conditions of 37 °C. The complex has Mg2+-dependent ATPase activity and can prevent the aggregation of citrate synthase. It promotes a high-yield refolding of guanidinium-chloride-denatured rhodanese in a nucleotide-dependent manner. ATP binding is sufficient to effect folding, but ATP hydrolysis is not essential.

Abbreviations used: TCP-1, T complex polypeptide-1; CCT, chaperonin containing TCP-1; Mm-cpn, Methanococcus maripaludis chaperonin; p[NH]ppA, adenosine 5′-[β,γ-imido]triphosphate; GdmCl, guanidinium chloride; DTT, dithiothreitol.

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Author notes

The nucleotide sequence data reported for the Methanococcus maripaludis chaperonin gene will appear in DDBJ, EMBL, GenBank® and GSDB Nucleotide Sequence Databases under the accession number AY099402.