Identification and bioinformatic analysis of a putative calcium-dependent protein kinase (CDPK6) from Toxoplasma gondii.

ABSTRACT

Toxoplasma gondii is recognized as an opportunistic human pathogen with a worldwide distribution. Development of effective vaccines is considered the only ideal way to control T. gondii infection. However, only one live vaccine is commercially available for use in sheep and goats. Therefore, the identification of more effective antigenic proteins is very important. In this study, we identified a novel putative calcium-dependent protein kinase of T. gondii, TgCDPK6, and further analyzed its potential antigenicity using a bioinformatic approach. The physical and chemical characteristics, transmembrane domain, epitopes, advanced structure, and functional sites of TgCDPK6 were predicted by multiple bioinformatic approaches. Twenty-six post-translational modification sites were identified in the protein. The secondary structure showed that 58.35% amino acids of TgCDPK6 are exposed to the solvent interface, and the high hydrophilic domains were distributed in amino acid positions 21-59, 68-81, 156-205, 245-271, 280-294, 297-324, 334-356, 367-393, 474-498, and 543-553. The advanced structure of TgCDPK6 was developed by a homology modeling method and was validated by PROCHECK, which showed that most amino acid residues were in the most favored regions. Using these analyses, 10 potential epitopes were predicted. The results indicated that TgCDPK6 could be a vaccine candidate antigen against T. gondii.