CLONING, SEQUENCING AND TRANSCRIPT ANALYSIS OF THE GENE ENCODING FORMYLMETHANOFURAN-TETRAHYDROMETHANOPTERIN FORMYLTRANSFERASE FROM THE HYPERTHERMOPHILIC METHANOTHERMUS-FERVIDUS

The formylmethanofuran: tetrahydromethanopterin formyltransferase (FTR ) from Methanothermus fervidus was partially purified and its N-termin al amino acid sequence determined. Using as probe a mixture of oligonu cleotides derived from the FTR N-terminus, the corresponding gene (ftr ) was cloned and sequenced. The ftr gene codes for 297 amino acids, co rresponding to a molecular mass of 31836 daltons, in contrast to the 4 1000 daltons estimated for the protein by sodium dodecylsulphate-polya crylamide gel electrophoresis. The deduced amino acid sequence of the hyperthermophilic FTR from M. fervidus is 76% identical to the thermop hilic FTR from Methanobacterium thermoautotrophicum and has a larger n umber of lysine residues. A putative ATP-binding site of the FTR is re ported. The size of the ftr mRNA was estimated as 1000 nucleotides ind icating monocistronic transcription of the 891 bp gene. The ftr mRNA s tarts 27 bp downstream of the centre of a putative archaeal box A moti f and terminates at an oligo-dT stretch. In vitro transcription of the ftr gene, utilizing a transcription system developed for the distantl y related Sulfolobus shibatae, is discussed with respect to the functi onal conservation of the basal transcription apparatus of Archaea.