The tubulin genes of the human malaria parasite Plasmodium falciparum, their chromosomal location and sequence analysis of the α-tubulin II gene

We report the isolation and sequencing of genomic clones encompassing the entire α-tubulin II gene from the human malaria parasite Plasmodium falciparum. This gene is close related to, but significantly different from the α-tubulin I gene that we have described previously [3]. These two genes represent the entire complement of α-tubulin sequences in this organism and are expressed in a stage-specific manner. The α-II gene is present as a single copy and encodes a tubulin molecule with a predicted length of 450 amino acid residues (49.7 kDa). Like the α-I gene, it contains two introns, which are in identical positions to those of α-I, but are about one-third smaller. The deduced α-II protein is very similar to α-tubulin I (94.2% amino acid identity), except for notable differences across residues 40-45. In addition, unlike the great majority of α-tubulin genes (including α-I), α-II does not encode a terminal tyrosine residue. Using pulsed field gel electrophoresis we demonstrate that the two α-tubulin genes, together with the single β-tubulin gene, are unlinked, all residing on different chromosomes. We assign α-I to chromosome 9, α-II to chromosome 4 and β-tubulin to chromosome 10.