In silico functional prediction and characterization of selected Theileria parva hypothetical proteins

Abstract

Cattle theileriosis is infamous for hampering the economic development of south, central and east African countries due to exorbitant numbers of cattle mortalities. The disease is caused by Theileria parva, an important tick-transmitted haemoprotozoan parasite that belongs to the phylum Apicomplexa. Infection of cattle with cattle-derived T. parva isolates is responsible for East Coast fever while infections by buffalo-derived isolates results in Corridor disease. A transcriptome study comparing two T. parva isolates, representing cattle- and buffalo-derived parasites, identified 1089 differentially expressed transcripts (DETs). Analysis of DETs revealed 593 (54.4%) hypothetical proteins (HPs). These proteins are believed that they could be crucial in understanding the diseases caused by T. parva infections. Thus, this study purposed to characterize these proteins. The initial screening using sequence similarity searches led to designation of sequence descriptions for 284 HPs; this report focuses on the analysis of the remaining 309. Applying an integrated bioinformatics approach including a variety of domains discovery tools, protein family classification systems and approaches that are based on amino acid sequence characteristic, as well as 3D structures predictions, functions of these HPs were predicted. Furthermore, information of functionally characterized homologs, subcellular localization and functional partners of HPs was considered in the analysis. Overall, n = 193 HPs were successfully annotated for function and some of these were virulent proteins, significant in the survival of the pathogen in the host. Subcellular localization revealed three HPs that could be investigated as possible therapeutic targets. Secretome analysis revealed 57 HPs containing signal peptides, suggesting possible interactions with the host. The results of this study will facilitate a better understanding of the mechanism of pathogenesis of cattle theileriosis caused by T. parva and development of more effective disease control strategies.