CLONING AND IDENTIFICATION OF THE SULFOLOBUS-SOLFATARICUS LRP GENE ENCODING AN ARCHAEAL HOMOLOG OF THE EUBACTERIAL LEUCINE-RESPONSIVE GLOBAL TRANSCRIPTIONAL REGULATOR LRP

The lrp gene of the extreme thermophilic archaeon Sulfolofus solfatari cus, encoding a homologue of the eubacterial global leucine-responsive regulatory protein, was identified by DNA sequencing and sequence com parisons on a 6.9-kb genomic fragment cloned into Escherichia coli. Th e S. solfataricus Lrp subunit is a 155-aa polypeptide that bears betwe en 24.5 and 29% sequence identity with eubacterial regulatory proteins of the Lrp/AsnC family and 30.6% and 25.8% with the archaeal homologu es of respectively Methanococcus jannaschii and Pyrococcus furiosus. T ranscription initiation from the strong S. solfataricus lrp promoter w as analyzed by primer extension mapping. The abundance of the S. solfa taricus lrp messenger strongly suggests that this protein might functi on in archaea as a global transcriptional regulator and genome organiz er, as proposed for E. coli Lrp, rather than as a local, specific regu latory protein. Our findings suggest the presence of a eubacterial typ e of regulatory mechanism in archaea, a situation that is noteworthy i ndeed, since the transcriptional machinery of archaea is more closely related to that of eukaryotes, whereas these latter apparently do not possess a homologue of Lrp. (C) 1997 Elsevier Science B.V.