To overcome the inflammatory response in its host, the cattle-feeding, brown ear tick secretes histamine-binding proteins into the feeding site. These proteins are beta-barrels with two internal binding sites: a high-affinity (H) site for histamine and a site (L) for which the natural ligand is unknown. Here we report a related protein (SHBP), secreted by a rodent- and cattle-feeding tick, that traps both histamine and serotonin. The histamine-binding H site is well conserved in SHBP, whereas residue changes in the L-like site are consistent with binding of the bulkier serotonin molecule. As histamine is a key inflammatory mediator in cattle, while serotonin takes on this role in rodents, the diversification of these tick proteins may reflect host adaptation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.