Localization of sequential antigenic determinants on bovine beta-casein with synthetic peptides and antisera from mouse, rabbit, and goat

The antigenic determinants of bovine beta-casein (beta-CN) were localized b y using twenty overlapping peptides encompassing the entire sequence of bet a-CN and anti-beta-CN antisera from outbred mouse, rabbit and goat. The pro file of the reactions was characteristic to the species, the dominant antig enic regions being 80-95, 143-158 and 195-209 in mouse, 1-16 in rabbit and 100-115 in goat. Regions 1-16, 100-115, 121-136 and 143-158 were antigenic in all three species. The number of antigenic regions recognized by goat wa s much fewer than that by mouse and rabbit, possibly because of the homolog y between bovine and goat beta-CN. A mixture of the twenty peptides could a bsorb about 50-60% of beta-CN specific antibodies from each species. Furthe rmore, the mouse and rabbit anti-beta-CN antibodies were also specific to t he phosphorylated regions. We therefore conclude that the major antigenic d eterminants on beta-CN would be largely sequential and include the phosphor ylated sites.