MOLECULAR-CLONING AND CHARACTERIZATION OF A SUPEROXIDE-DISMUTASE (SOD) GENE IN PNEUMOCYSTIS-CARINII

This work reports the isolation and characterization of a gene encodin g a superoxide dismutase (SOD, EC.1.15.1.1.) from Pneumocystis carinii derived from rat. Sense and antisense oligonucleotides, deduced from SOD amino acid sequences from a wide variety of organisms, allowed amp lification of a 669 bp genomic DNA fragment specific to this P. carini i. RACE-PCR was used to obtain the major part of the complementary DNA ; the 5'- and 3'-genomic regions were obtained respectively from a Mbo I subgenomic library and from an amplified fragment using oligonucleot ides designed from the cDNA sequence. Comparison of genomic and cDNA s equences showed an open reading frame of 660 bp interrupted by seven s mall introns. The deduced amino acid sequence contained 220 residues. Protein sequence alignment demonstrated the highest homology (50.5% id entity; 70.3% similarity) with Saccharomyces cerevisiae manganese-SOD (MnSOD) suggesting that P. carinii SOD belongs to the mitochondrial Mn SOD group. A putative targeting peptide found at the 5'-end of the P. carinii SOD sequence also suggested its mitochondrial localization.