THE MULTIFUNCTIONAL FOLIC-ACID SYNTHESIS FAS GENE OF PNEUMOCYSTIS-CARINII APPEARS TO ENCODE DIHYDROPTEROATE SYNTHASE AND HYDROXYMETHYLDIHYDROPTERIN PYROPHOSPHOKINASE

We describe the cloning of a multifunctional folic acid synthesis (fas) gene from Pneumocystis carinii. The nucleotide sequence contains an open reading frame interrupted by three introns, that encodes a protein of 740 amino acids with an M(r) of 97 278. The predicted Fas protein has homology to two enzyme domains, dihydropteroate synthase and 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase, both of which are involved in folate synthesis, and at least one other region of unknown function.