CITRATE SYNTHASES FROM THE ARCHAEA

Citrate synthase catalyses the entry of carbon into the citric acid cy cle, and therefore it occupies a key position in central metabolism th roughout the majority of Bacteria, Eukarya and Archaea. We have chosen citrate synthase as a model protein in which to study the relationshi p between enzyme structure, function, and stability to environmental e xtremes. Our strategy has been to clone, sequence and express the gene s encoding the enzyme from Archaea that span the phenotypic range of t emperature and halophilicity, thereby producing sufficient quantities of protein for detailed structural studies. Having previously cloned, sequenced and expressed the gene encoding the citrate synthase from Th ermoplasma acidophilum, we now report the purification, characterisati on and N-terminal sequencing of citrate synthase from Pyrococcus furio sus, These sequences are aligned with the N-termini of citrate synthas es from Sulfolobus solfataricus and Haloferax volcanii and with the en zymes from Bacteria and Eukarya.