Secondary structure of bovine alpha(S2)-casein: Theoretical and experimental approaches

Circular dichroism and Fourier transform infrared spectroscopy of bovine al pha (S2)-casein both report a 24 to 32% content of alpha -helix. A consensu s of sequence based predictions for alpha -helix suggests a Lys(77)-Gln(91) helix within the sequence (Ser(61)-Arg(125)). This motif is repeated at (S er(143)-Leu(207)), and this region contains a longer Thr(145)-Leu(177) pred icted alpha -helix. A short, seven member alpha -helix may also organize th e N-terminal peptide that precedes the first phosphoserine [-Srp-](3) clust er. As was found for other caseins studied by these spectroscopic methods, a high degree of extended beta -sheet (similar to 30%) and turns (25 to 30% ) are predicted for alpha (S2)-casein.