Análisis estructural de algunas proteínas de unión a calcio en Giardia lamblia y evaluación de su patrón de expresión (mRNA)

Abstract

In this paper the structure of eight possible calcium binding proteins in Giardia lamblia was analyzed and the pattern of expression at the transcriptional level of the genes encoding these proteins was evaluated. Bioinformatics tools were used for the structural analysis. It was possible to identify potential homologous proteins, detect calcium-binding domains in the sequences and predict alpha helices and coil regions, which are characteristic of the EF-hand calcium binding domain. Additionally, the three-dimensional structure of the target proteins was modeled and for five of them (Hipot 16, Hipot 64, PCD, DYN y PP2A 453) it was possible to obtain reliable models where calcium binding sites were located. The models for the remaining three proteins (PP2A 638, PP2A 892 y PP2A 764) were not accurate enough so it was not possible to locate calcium binding sites on the structures, although these were predicted in the sequences. On the other hand, the expression pattern of mRNA of the genes encoding the target proteins was evaluated during encystation of the parasite by using RT-PCR. To accomplish that, RNA extracted from synchronized Giardia lamblia parasites at different encystation times (0, 6, 12 and 24 hours) was used and the results of the amplification after the RT-PCR were quantified by densitometry. It was found that all the genes are transcribed during the encystation process following differential patterns. Moreover, some of the expression patterns could be associated with specific events taking place during the encystation process. Taking together, these results allowed a preliminary approach to the possible role of these proteins in the parasite.