CLONING AND CHARACTERIZATION OF THE GENE ENCODING PYRUVATE PHOSPHATE DIKINASE FROM GIARDIA-DUODENALIS

This paper reports the cloning and molecular characterization of the g ene encoding pyruvate phosphate dikinase (PPDK) from Giardia. The ORF is 2652 nucleotide residues in length and not interrupted by introns. The gene appears to exist as a single copy in the genome and predicts a 97 629 Da protein containing 884 amino acid residues. Comparison of the deduced Giardia PPDK sequence with those of homologous enzymes fro m other organisms revealed high sequence similarities and the presence of various conserved domains known to be essential for substrate bind ing and catalysis. Analysis of the ppdk gene and 19 other protein-codi ng genes from the protist revealed no typical TATA boxes, positioned a t around -30, but the presence of two novel consensus sequence motifs in the 5' flanking regions. One is an AT-rich element immediately prec eding the translation initiation codon and the other a 14-bp box cente red at -30. These shared consensus sequence patterns present in the 5' flanking region of Giardia genes are suggested to play a role in the control of transcription initiation.