This family of proteins is a Eukaryotic family of surface antigens. One of the better characterised members of the family is the sporulated TA4 antigen. The TA4 gene encodes a single polypeptide of 25 kDa which contains a 17 and a 8 kD polypeptide [1].

1: Characterization of a surface antigen of Eimeria tenella sporozoites and synthesis from a cloned cDNA in Escherichia coli. Brothers VM, Kuhn I, Paul LS, Gabe JD, Andrews WH, Sias SR, McCaman MT, Dragon EA, Files JG; Mol Biochem Parasitol. 1988;28:235-247. PMID:3290678