AN ARCHAEAL GENE UPSTREAM OF GRPE DIFFERENT FROM EUBACTERIAL COUNTERPARTS

In some eubacteria with a dnaK locus in which grpE is close upstream o f dnaK, grpE is preceded by an open reading frame (orf) believed to be a heat-shock gene. We also found an orf orf16, upstream of grpE in th e archaeon Methanosarcina mazei S-6, but this gene differs from the eu bacterial counterpart: it is shorter, does not respond to a temperatur e upshift as heat-shock genes do, and the deduced protein Orf16, does not resemble the proteins coded by the eubacterial equivalents. orf16 is expressed monocistronically, with a transcription initiation site 2 4 bases upstream of the translation start codon, 22 bases downstream o f a putative promoter identical to the consensus promoter for genes in methanogens. This initiation site is used by heat-shocked and non-hea t-shocked cells in the two morphologic stages of M. mazei S-6 tested, i.e., packets and single cells. Three transcription termination sites were identified, one of which is detectable only in non-heat-shocked c ells. Data from comparative analyses of the Orf16 deduced amino acid s equence and those of other known proteins, as well as the apparent bio chemical characteristics of Orf16, suggest that the latter is a membra ne molecule.