Evidence for a common epitope between bovine alpha-lactalbumin and beta-lactoglobulin

The aim of this work was to check and quantify any cross-reactivities among the main bovine whey proteins, utilizing purified polyclonal antibodies against bovine beta-lactoglobulin, alpha-lactalbumin and serum albumin, and to identify possible common epitope(s). Purified polyclonal anti-bovine beta-lactoglobulin antibodies show 10% cross-reactivity with bovine alpha-lactalbumin, both in its native and its denatured form. A continuous stretch of four amino acids common to alpha-lactalbumin and beta-lactoglobulin that might be responsible for this cross-reactivity has been identified. Cross-reactivity between this antibody and bovine serum albumin is, on the contrary, negligible. Purified polyclonal anti-bovine alpha-lactalbumin and anti-serum albumin antibodies do not cross-react.