Molecular cloning, Genomic organization and evolution of the Toxoplasma gondii kazal inhibitors TgPI-1 and TgPI-2, and characterization of novel closely linked genes

MARINA CLEMENTE, LETICIA PERALTA, CAROLINA DALMASSO, SERGIO ANGEL

Mendoza, Argentina

Congreso; VII Congreso Argentino de Protozoología y Enfermedades Parasitarias; 2005

VII Congreso Argentino de Protozoología y Enfermedades Parasitarias

Toxoplasma gondii kazal inhibitors TgPI-1 and TgPI-2 genes were mapped on parasite genome. They are linked, separated by ~2450-bp. A gene (TgCyt16) encoding a  cytoplasmic protein of 16-kDa is located in the inter TgPIs region. In addition, another gene (TgSNF) was located sharing the 3’ termini region of TgPI-2 gene. The deduced aminoacidic sequence of TgSNF retrieved similarity to sodium-dependent transporter of sodium neurotransmitter symporter family. The sequence analysis indicated that this protein could have 12 integral transmembrane regions. Both TgPI-1 and TgPI-2 showed seven deduced introns and eight  exons, four of them encoding a complete kazal domain. Phylogenetical analysis of TgPI-1 and TgPI-2 DNA sequence encoding domains showed that PI-1 domains are clustered in a group, whereas those of PI-2 are clustered in another one. Similar analysis using intron sequences showed that they clustered at random rather than as inter- or intra-gene counterparts. Genetic distances, based on dN/dS ratios for each pair of TgPIs and their Neospora caninum counterparts (NcEST-1 and NcEST-2,) kazal domain sequences, showed PI-2 faster evolution than PI-1 observed by exon domains. Implications of these data in the inter- and intra kazal inhibitor evolution is discussed.