Bioinformatic prediction and characterization of the SNARE protein family in the divergent protozoan Giardia lamblia

QUIROGA, R.; ELÍAS, E.V; PRUCCA, C.G.; LUJÁN H.D.

Huerta Grade. Córdoba. Argentina

Congreso; XXI Reunión Anual de la Sociedad Argentina de Protozoologia.; 2006

Giardia lamblia is an early braching protist with unusual eukaryotic characteristics, including the absence of a morphologically evident Golgi apparatus. Altought both constitutive and regulated pathways for protein secretion exist in Giardia spp., little is known about the molecules and mechanisms specifically involved in vesicular docking and fusion. In higher eukaryotes, the SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins play essential roles in these processes through the formation of complexes between proteins present on donor and target membranes. Here we present results from a complete bioinformatic analysis of the Giardia genome for SNARE encoding genes, the validation of this data through Hidden Markov Model construction and evaluation, as well as the prediction of the 3D protein structure trough modeling by satisfaction of spatial restraints. We also classified Giardia SNARES into Qa, Qb, Qc and R subclasses. The characterization of these proteins in Giardia allowed a more sensitive and effective prediction of this protein family in other eukaryotes who have completely sequenced genomes but do not have a complete set of SNARE proteins characterized. The description of all these novel SNARES in ancient eukaryotes will allow a detailed study of the evolution of this protein family and more specifically of the SNAP proteins (proteins with two SNARE domains and no transmembrane domain) due to the fact that they are present in only some of the aforementioned organisms and it has been proposed that SNAP proteins appeared during eukaryotic evolution by fusion of two SNARE proteins.