Solution Structures of Casein Peptides: NMR, FTIR, CD, and Molecular Modeling Studies of αs1-Casein, 1–23

• Published in: Journal of Protein Chemistry 2001-07, Vol.20 (5), p.391-404
• Main Authors: Malin, Edyth L., Alaimo, Michael H., Brown, Eleanor M., Aramini, James M., Germann, Markus W., Farrell, Harold M., McSweeney, Paul L. H., Fox, Patrick F.
• Format: Article
• Language: English
• Subjects: Casein; Circular dichroism; Dichroism; Fourier transforms; Infrared spectroscopy; Micelles; Modelling; Molecular biology; Molecular dynamics; Molecular modelling; NMR; Nuclear magnetic resonance; Peptides; Polyproline; Proteins
• ISSN: 0277-8033; 1572-3887; 1573-4943
• DOI: 10.1023/A:1012232804665

To determine its potential for interacting with other components of the casein micelle, the N-terminal section of bovine αs1-casein-B, residues 1-23, was investigated with nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopies, and molecular modeling. NMR data were not consistent with conventional α-helical or β-sheet structures, but changes in N-H proton chemical shifts suggested thermostable structures. Both CD and FTIR predicted a range of secondary structures for the peptide (30–40% turns, 25–30% extended) that were highly stable from 5°C to 25°C. Other conformational elements, such as loops and polyproline II helix, were indicated by FTIR only. Molecular dynamics simulation of the peptide predicted 32% turns and 27% extended, in agreement with FTIR and CD predictions and consistent with NMR data. This information is interpreted in accord with recent spectroscopic evidence regarding the nature of unordered conformations, leading to a possible role of αs1-casein (1–23) in facilitating casein-casein interactions.