Four-Dimensional Heteronuclear Triple-Resonance NMR Spectroscopy of Interleukin-1β in Solution

Abstract

A method is presented that dramatically improves the resolution of protein nuclear magnetic resonance (NMR) spectra by increasing their dimensionality to four. The power of this technique is demonstrated by the application of four-dimensional carbon-13—nitrogen-15 ( 13 C- 15 N)—edited nuclear Overhauser effect (NOE) spectroscopy to interleukin-1β, a protein of 153 residues. The NOEs between NH and aliphatic protons are first spread out into a third dimension by the 15 N chemical shift of the amide 15 N atom and subsequently into a fourth dimension by the 13 C chemical shift of the directly bonded 13 C atoms. By this means ambiguities in the assignment of NOEs between NH and aliphatic protons that are still present in the three-dimensional 15 N-edited NOE spectrum due to extensive chemical shift overlap and degeneracy of aliphatic resonances are completely removed. Consequently, many more approximate interproton distance restraints can be obtained from the NOE data than was heretofore possible, thereby expanding the horizons of three-dimensional structure determination by NMR to larger proteins.