Abstract
The biosynthesis of dTMP has been studied in cell extracts of two different members of the domain Archaea, Methanosarcina thermophila and Sulfolobus solfataricus. In M. thermophila, the dTMP was formed from dUMP and [methylene-2H2]-5,10-methylenetetrahydrosarcinapterin generated in situ from added [methylene-2H2] formaldehyde and the tetrahydrosarcinapterin present in the cell extract. In S. solfataricus, the 5,10-methyl-enetetrahydro derivative of a synthetic fragment of sulfopterin, the modified folate present in these cells, served as the C1 donor. These data indicate that the Archaea thymidylate synthases carry out the same basic reaction which occurs in other organisms but use the 5,10-methylenetetrahydro derivatives of modified folates as C1 donors.