Isoprenoid synthesis gene for geranylgeranyl diphosphate synthase from a hyperthermophile, Pyrococcus sp. strain OT3.

Pyrococcus sp. strain OT3, a hyperthermophilic archaeon that was isolated by the authors was found to contain tetraether lipid mainly in the membrane lipid, which was quite different from the other hyperthermophiles (Masuchi et al. 1997). Those isoprenoids are synthesized by a family of isoprenyl diphosphate synthases from isopentenyl diphosphate to allylic diphosphates. The gene that encodes one of these families, geranylgeranyl diphosphate synthase (GGPPSase), from this strain was cloned and sequenced. This coding gene has a 960-bp (320aa) sequence. The putative Shine-Dalgarno sequence was six bases upper of start codon, exactly the same as Methanobacterium thermoautotrophicum, a methnogenic thermophile. Comparison of the amino acid sequence of 13 organisms including Eukarya, Bacteria, and Archaea showed that Archaea strains including Pyrococcus sp. strain OT3 consisted of a separate group from the others, but five conservative regions are very homologous.