STRUCTURE OF THE GENES ENCODING THE ALPHA-SUBUNITS AND BETA-SUBUNITS OF CASTOR PYROPHOSPHATE-DEPENDENT PHOSPHOFRUCTOKINASE

Full-length genomic clones encoding the alpha- and beta-subunits of th e pyrophosphate-dependent phosphofructokinase (PFP) from the castor pl ant have been isolated and sequenced. The gene (PFP alpha) encoding PF P alpha is approx. 5.8 kb in length and contains 19 exons, which colle ctively encode a protein of 617 amino acids (aa) having a deduced M(ta u), of 67 360. PFP beta is approx. 4.6-kb long and contains 16 exons, Together, these exons encode a protein (PFP beta), of 552 aa with a de duced M, of 60114. The intron-exon splice junctions in both genes cont ain the consensus sequences typical for plants, An alignment of intron placement in castor PFP alpha and PFP beta with introns in the 5' por tion of the gene encoding the ATP-dependent phosphofructokinase (PFK) from rabbit muscle, indicates that only one intron occupies the same p osition in all three genes. Furthermore, within castor PFP alpha( and PFP beta, only two introns are identically placed. Within the promoter regions of castor PFP alpha and PFP beta, there are short sequences h aving high homology to each other (up to 65%). The results demonstrate , for the first time, that there is little homology between PFP and PF K, nor are PFP alpha and PFP beta closely related. This lack of homolo gy suggests PFP did not evolve from PFK, but rather, that PFP and PFK have probably evolved from a common ancestral gene.