Secondary structure of bovine αS2-casein: Theoretical and experimental approaches

Abstract

Circular dichroism and Fourier transform infrared spectroscopy of bovine αS2-casein both report a 24 to 32% content of α-helix. A consensus of sequence based predictions for α-helix suggests a Lys77-Gln91 helix within the sequence (Ser61-Arg125). This motif is repeated at (Ser143-Leu207), and this region contains a longer Thr145-Leu177 predicted α-helix. A short, seven-member α-helix may also organize the N-terminal peptide that precedes the first phosphoserine [-Srp-]3 cluster. As was found for other caseins studied by these spectroscopic methods, a high degree of extended β-sheet (∼30%) and turns (25 to 30%) are predicted for αS2-casein.