2-DIMENSIONAL H-1-NMR AND CD STRUCTURAL-ANALYSIS IN A MICELLAR MEDIUMOF A BOVINE ALPHA(S1)-CASEIN FRAGMENT HAVING BENZODIAZEPINE-LIKE PROPERTIES

The conformation of the benzodiazepine-like decapeptide, YLGYLEQLLR, c orresponding to residues 91-100 of bovine alpha(S1)-casein, has been e xamined in SDS micelles using CD, two-dimensional H-1-NMR and restrain ed molecular-dynamics simulation, Evidence is presented that the decap eptide adopts a rigid structure in water/SDS micellar medium, but not in water or dimethylsulfoxide. The three-dimensional structure, consis tent with the proton-proton distances obtained from the quantitative a nalysis of the two-dimensional NOEs, was generated by restrained energ y minimization and molecular-dynamics simulation. In water/SDS micella r medium, YLGYLEQLLR adopts an amphipathic helicoid structure with dis tinct hydrophobic and hydrophilic faces. The relative disposition of t he tyrosine aromatic rings was compared with that of the aromatic ring s in the benzodiazepines.