CLONING OF THE TRIOSEPHOSPHATE ISOMERASE GENE OF PLASMODIUM-FALCIPARUM AND EXPRESSION IN ESCHERICHIA-COLI

A major supply of energy in the rapidly multiplying intraerythrocytic Plasmodium falciparum is from the glycolytic pathway. We have isolated the cDNA and genomic clones of the glycolytic enzyme, triosephosphate isomerase (TPI) by polymerase chain reaction (PCR). Degenerate oligon ucleotides obtained by reverse translation of conserved polypeptide se quences derived from TPIs of other organisms, were used to prime PCR o n P. falciparum DNA. The P. falciparum TPI gene is interrupted by a si ngle intron which divides the coding region into two exons. The coding region encodes a protein of 248 amino acids which is of the same size as TPIs from other organisms and shares 42-45% homology with other kn own eukaryotic TPIs. On comparison with human TPI the catalytic domain was found to be highly conserved, while significant variations occurr ed at the other regions in the protein sequence. The P. falciparum TPI gene was cloned into the expression vector pTrc99A and hyperexpressed as an unfused protein in Escherichia coli. The 28-kDa protein was sho wn to be catalytically active.