Fractionation of bovine caseins by reverse phase high performance liquid chromatography: identification of a genetic variant

Abstract

Samples of reduced whole casein from genetically typed individual cows were quantitatively separated into their main components, αsl-, αs2-, β- and κ-caseins by reverse phase high performance liquid chromatography (RP-HPLC) using a mobile phase of phosphate-buffered aqueous propan-2-ol containing sodium dodecyl sulphate and an octadecylsilyl stationary phase. One casein sample was found to give two peaks of β-casein of approximately equal areas. RP-HPLC of tryptic digests of the two separated peak fractions gave identical patterns with the exception of one peptide peak with different retention times. Amino acid analyses performed on both fractions showed that they corresponded to peptide 114–169 of β-casein A1. The atypical β-casein differed from the typical one by a Pro→Leu substitution in region 114–169.