MOLECULAR-CLONING OF ACTIN GENES IN TRICHOMONAS-VAGINALIS AND PHYLOGENY INFERRED FROM ACTIN SEQUENCES

The parasitic protozoan Trichomonas vaginalis is known to contain the ubiquitous and highly conserved protein actin. A genomic library and a cDNA library have been screened to identify and clone the actin gene( s) of T. vaginalis. The nucleotide sequence of one gene and its flanki ng regions have been determined. The open reading frame encodes a prot ein of 376 amino acids. The sequence is not interrupted by any introns and the promoter could be represented by a 10 bp motif close to a con sensus motif also found upstream of most sequenced T. vaginalis genes. The five different clones isolated from the cDNA library have similar sequences and encode three actin proteins differing only by one or tw o amino acids. A phylogenetic analysis of 31 actin sequences by distan ce matrix and parsimony methods, using centractin as outgroup, gives c ongruent trees with Parabasala branching above Diplomonadida.