MOLECULAR-CLONING, SEQUENCING, AND HETEROLOGOUS EXPRESSION OF A NOVELZINC-CONTAINING FERREDOXIN GENE FROM A THERMOACIDOPHILIC ARCHAEON SULFOLOBUS SP STRAIN-7

The gene encoding a novel zinc-containing ferredoxin from a hypertherm ophilic and acidophilic archaeon (archaebacterium) Sulfolobus sp. stra in 7 was cloned and sequenced. The DNA sequence predicts a 103 residue protein after removal of N-terminal methionine, which is in good agre ement with the results of the protein analysis. Surprisingly, the resi dues responsible for binding a zinc atom were conserved among three ot her thermoacidophilic archaea. A common sequence stretch VXGXHXGHX(8-1 7)PXXLGXHGTX(38). (56)KXDPV is proposed as a new zinc-binding motif, w here 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 Sulfo lobus sp, strain 7 cells by several criteria so far investigated excep t that the methylation of the 29th lysine was suppressed. (C) 1996 Aca demic Press, Inc.