Molecular cloning, sequencing, and heterologous expression of a novel zinc-containing ferredoxin gene from a thermoacidophilic Archaeon Sulfolobus sp. strain 7.

The gene encoding a novel zinc-containing ferredoxin from a hyperthermophilic and acidophilic archaeon (archaebacterium) Sulfolobus sp. strain 7 was cloned and sequenced. The DNA sequence predicts a 103 residue protein after removal of N-terminal methionine, which is in good agreement with the results of the protein analysis. Surprisingly, the residues responsible for binding a zinc atom were conserved among three other thermoacidophilic archaea. A common sequence stretch VXGXHXGHX8-17PXXLGXHGTX38-56KXDPV is proposed as a new zinc-binding motif, where three histidines and an aspartic acid are ligated to a zinc atom. The ferredoxin gene was expressed in Eschericia coli. The recombinant ferredoxin was indistinguishable from the protein purified from Sulfolobus sp. strain 7 cells by several criteria so far investigated except that the methylation of the 29th lysine was suppressed.