Molecular characterization and evolutionary analysis of horse BAFF-R, a tumor necrosis factor receptor related to B-cell survival.

B-cell survival depends on signals induced by B-cell activating factor (BAFF) that binds to the BAFF receptor (BAFF-R). Herein, a BAFF-R homolog was identified in a horse (Equus caballus). The horse BAFF-R gene, located on chromosome 28, spans 1444 base pairs and encodes a 183-amino acid protein. The protein is structurally conserved, in which the DxL motif plays an important role in binding to BAFF. Furthermore, the horse BAFF-R extracellular domain was expressed and purified, which specifically bound to His6-sBAFF and had the capability of blocking the function of His6-sBAFF in vitro. Finally, evolutionary analyses indicated that some codon sites of BAFF-R evolve with positive selection and that the genetic relationship among a horse, Chiroptera, and Caniformia are the closest.