Oligonucleotide primers were used to amplify DNA sequences from a plasma membrane cation transporting ATPase gene and a transcription factor IID (TFIID) gene from Pneumocystis carinii genomic DNA. The entire P. carinii ATPase gene was cloned from a genomic library by hybridization to the PCR-amplified DNA product. The nucleotide sequence of the gene contained a 2,799 base-pair open reading frame that encoded a 102,274 dalton protein composed of 933 amino acids. The P. carinii ATPase protein was 69-74% identical to four fungal proton pumps but less than 35% identical to protozoan and mammalian cation transporting ATPase genes or the Ca++ ATPases of Saccharomyces. The nucleotide sequence of a portion of the TFIID gene could be translated to produce a peptide of 53 amino acids in two regions of the sequence, interrupted by a 45 bp intron. The predicted TFIID amino acid sequence was identical to yeast TFIID genes in this region.