Stereospecific assignment of beta-methylene protons in larger proteins using 3D 15N-separated Hartmann-Hahn and 13C-separated rotating frame Overhauser spectroscopy

Abstract

3J alpha beta coupling constants and complementary nuclear Overhauser data on the intraresidue C alpha H-C beta H distances form an essential part of the data needed to obtain stereospecific assignments of beta-methylene protons in proteins. In this paper we show that information regarding the magnitude of the 3J alpha beta coupling constants can be extracted from a semi-quantitative interpretation of relative peak intensities in a 3D 15N-separated 1H-1H Hartmann-Hahn 1H-15N multiple quantum coherence (HOHAHA-HMQC) spectrum. In addition, we demonstrate that reliable information on the intraresidue C alpha H-C beta H distances, free of systematic errors arising from spin diffusion, can be obtained from a 3D 13C-separated 1H-1H rotating frame Overhauser effect 1H-13C multiple quantum coherence (ROESY-HMQC) spectrum. The applicability of these experiments to larger proteins is illustrated with respect to interleukin-1 beta, a protein of 153 residues and 17.4 kDa molecular weight.