Theileria annulata is an apicomplexan parasite causing tropical theileriosis with high mortality in cattle in different areas, especially in Iran. Theileria annulata surface protein (TaSp) is an antigenic protein and it can be a suitable antigen for serological diagnostic tool. In this study, bioinformatic analysis was performed in order to predict the primary biochemical characteristics of the TaSp including physicochemical, antigenic and allergenic profiles, transmembrane domain, subcellular localization, posttranslational modification (PTM) sites, secondary and 3D structure, tertiary model refinement and prediction of linear B-cell epitopes. Our survey showed that the 35.46 kDa of TaSp has 314 amino acids with a MW of 35450.07 Da and theoretical pI of 4.68. The protein possessed 47 negatively charged (Asp + Glu) and 25 positively-charged (Arg + Lys) residues. The total number of atoms was 4917 having extinction coefficient of 32025 M− 1 cm− 1 at 280 nm measured in water. The estimated half-life for TaSp was as follows: 30 h (mammalian reticulocytes, in vitro), > 20 h (yeast, in vivo) and > 10 h (Escherichia coli, in vivo). This survey demonstrated that the protein has high antigenicity and it is not an allergen. TaSp has 38 phosphorylation sites and 6 acylation sites. Also, Transmembrane domains and subcellular localization of TaSp were 43.5 %: endoplasmic reticulum, 26.1 %: plasma membrane, 13.0 %: mitochondrial, 4.3 %: vacuolar, 4.3 %: vesicles of secretory system, 4.3 %: Golgi and 4.3 %: extracellular. On the other hand, Secondary structure prediction in the TaSp sequence showed to 74 (2357%) alpha helix, 189 (60.19%) random coil and 51 (16.24%) extended strands. Also, 3D structure of this protein was predicted and refined. Prediction of linear B-cell epitopes of TaSp using different servers determined at least six high-ranked epitopes. According to that the cross-reactivity between Theileria and other species of parasites is the main problem for serological detection of Theileriosis. so, the sensitivity and specificity of serological diagnostic methods can be improved for specific diagnosis of Theileria, using special epitopes with high specificity and antigenicity.
