Genome-wide screening, identification and analysis of BAR domain-containing proteins in Toxoplasma gondii

Toxoplasma gondii is an important zoonotic pathogen that infects nucleated cells in all warm-blooded animals, and affects about one-third of the world's population. The treatment for T. gondii relies on drugs, but there is no specific cure. The discovery, identification and understanding of key protein families of T. gondii are of great significance for candidate antigen screening, vaccine development, and novel prevention and control program. The Bin, amphiphysin and Rvs (BAR) superfamily is a category of proteins with the BAR domain, which plays an important role in membrane tubulation and constriction during vesicle formation in mammalian cells, and is essential for material transport. However, the information of BAR proteins in T. gondii is not comprehensive. In present study, we screened and identified four BAR domain-containing proteins (Bcps), including TGGT1_259720, TGGT1_320760, TGGT1_232180 and TGGT1_224070 in the T. gondii genome using HMM search and local blast. All above-mentioned Bcps contained the BAR domain, and the 3D structures present the typical crescent shaped helical dimer of BAR. The classification of BAR domains was analyzed by evolutionary tree clustering, and it was found that TGGT1_259720 belonged to F-BAR and the other three belonged to N-BAR. The phylogenetic analysis of four protozoa showed that the Bcps of T. gondii were the closest relative to those of N. caninum, which was consistent with the result of collinearity analysis among species. Moreover, conserved motif and gene composition analysis further confirmed that these closely related proteins are more similar in these structures. The prediction of interacting proteins also showed that Bcps had strong interaction with the key proteins of vesicle transport. The quantification of BAR genes by qPCR showed that these BAR genes were expressed during the growth and proliferation of T. gondii, and the expression patterns were different under different nutritional conditions with the increase of FBS concentration gradient, indicating that these genes played different roles.