NMR studies of myelin basic protein. XIII. Assignment of histidine residues in rabbit, bovine and porcine proteins

Abstract

Myelin basic protein from three species (rabbit, cow and pig) and peptides from enzymatic digests or cleavage of the proteins have been examined in aqueous solutions by proton nuclear magnetic resonance (NMR) at 400 MH z. The ε 1-CH and δ 2-CH resonances of all the histidine residues in the three proteins have been assigned and the p K values have been measured. The heterogeneity of chemical shifts among these resonances can be variously ascribed to persistent localized secondary structures and to effects arising from charged side-chains, particularly those of aspartic acid residues, and from side-chains of aromatic moieties.