Studies of .beta.-sheet structure in lysozyme by proton nuclear magnetic resonance. Assignments and analysis of spin-spin coupling constants

Abstract

Resonances of H.alpha., H.beta., and HN (amide) protons were assigned in the NMR spectrum for 10 residues in a region of .beta.-sheet structure of [hen egg] lysozyme. The assignments were achieved primarily by interpretation of nuclear Overhauser effects in conjunction with spin decoupling. The HN hydrogens involved in main-chain H.sbd.bonding exchanged slowly with D2O solvent, although one of the most slowly exchanging HN hydrogens is not classified as being involved in a H.sbd.bond in the crystal structure. Spin-spin coupling constants between H.alpha. protons and HN and H.beta. protons correlated well with values predicted from the crystal structure by means of the Karplus relationship. For no residues are the coupling constant discrepancies greater than 2.5 Hz. For the residues studied here the torsion angles .vphi. and .chi.1 defined in the crystal structure describe accurately, generally well within 20.degree., those for the average solution state.