immunology of infectious and parasitic diseases - XXXVII Congress ...

SAG2A PROTEIN OF Toxoplasma gondii SHOWS AN INTRINSICALLY
UNSTRUCTURED PROTEIN DOMAIN
ARLINDO GOMES DE MACÊDO JÚNIOR 1 , JAIR P. CUNHA-JUNIOR 1 ,
THYAGO H. S. CARDOSO 2,3 , MURILO V. SILVA 1 , FERNANDA M.
SANTIAGO 1 , JOÃO S. SILVA 4 , CARLOS P. PIROVANI 2 , DEISE A. O. SILVA 1 ,
JOSÉ R. MINEO 1 , TIAGO W. P. MINEO
1. Immunoparasitology Laboratory, Institute of Biomedical Sciences, Federal
University of Uberlândia (UFU), Uberlândia, Minas Gerais, Brazil. 2.
Biotechnology and Genetics Center, Santa Cruz State University/UESC, Bahia,
Brazil. 3. Department of Biochemistry, Escola Paulista de Medicina,
Universidade Federal de São Paulo, São Paulo, SP, Brazil. 4 School of
Medicine of Ribeirão Preto, São Paulo University/USP, São Paulo, Brazil.
Introduction Toxoplasmosis is a zoonosis caused by an intracellular parasite,
Toxoplasma gondii. Several studies have been performed in order to
understand the interactions between proteins of parasite and its host cells.
SAG2A is a 22 kDa protein that is mainly found in the surface of tachyzoites.
Additionally, It has been previously found to be serologically immunodominant
during the acute phase of toxoplasmosis. In the present work, our major aim
was to study the structure modeling demonstrated that SAG2A protein. Methods
To construct three-dimensional structures of SAG2A, modeling was based on
structures solved by X-ray crystallography or RMN and PSI-Blast. Recombinant
protein SAG2A full and without C-terminal region and tachyzoites of RH strain
of T. gondii were used in experiments with macrophages derived from mouse
bone marrow. Concentrations of IL-12 were measured by commercial ELISA
kits and nitric oxide production estimated from the concentration of nitrite by the
Griess method. Results Structure modeling demonstrated that SAG2A protein
possesses an unfolded C-terminal end forming a loop, characteristic of
intrinsically unstructured protein (IUP) domains, which also sheltered the known
immunodominant epitope. In addition, distinct conformations of the loop were
predicted within strain types of T. gondii, due to an additional glycine found in
type II strains, which induced the formation of a helical structure in the
immunodominant epitope region. Modeling of NcSAG2A, orthologue expressed
in Neospora caninum, confirmed similar overall structure of the orthologues,
although it may be noted that SAG2A from T. gondii presents a largely