NUCLEOTIDE-SEQUENCE OF A DNA REGION COMPRISING THE GENE FOR ELONGATION FACTOR-1-ALPHA (EF-1-ALPHA) FROM THE ULTRATHERMOPHILIC ARCHAEOTE PYROCOCCUS-WOESEI - PHYLOGENETIC IMPLICATIONS

The gene encoding elongation factor 1-alpha (EF-1-alpha, 1290 bp) of the ultrathermophilic, sulfur-reducing archaeote Pyrococcus woesei was localized within a Bg/II fragment of chromosomal DNA. Sequence analysis showed that the EF-1-alpha gene is the upstream unit of a three-gene cluster comprising the genes for ribosomal protein S10 (306 bp) and transfer RNA(ser) (GGA). The three genes follow each other immediately in the order EF-1-alpha.S10.tRNA(ser) after a putative promoter located 55 bp upstream of the EF-1-alpha gene. Alignment of the derived EF-1-alpha sequence with the corresponding sequences from Eukarya, Bacteria/organelles, and with available archaeal sequences (Sulfolobus, Thermococcus, Methanococcus, Halobacterium) showed that Pyrococcus EF-1-alpha is highly homologous (89% identity) to Thermococcus celer EF-1-alpha, both being strikingly more similar to eukaryotic EF-1-alpha than to bacterial EF-Tu. Unrooted dendrograms computed from aligned sequences by distance matrix and DNA parsimony methods, including evolutionary parsimony, showed the Archaea to be a monophyletic-holophyletic cluster closer to Eukarya than to Bacteria. Both distance matrix and DNA parsimony-although not evolutionary parsimony-support the partition of the known archaeal lineages between the kingdoms Crenarchaeota and Euryarchaeota, and the affiliation of the Pyrococcus-Thermococcus lineage to the Euryarchaeota, of which it is the most primitive offspring. A closer relation of Pyrococcus to Euryarchaeota than to Crenarchaeota was also inferred from sequence analysis of S10 ribosomal proteins.