Transverse relaxation optimized spectroscopy of NH2 groups in glutamine and asparagine side chains of proteins

Abstract

A transverse relaxation optimized spectroscopy (TROSY) approach is described for the optimal detection of NH₂ groups in asparagine and glutamine side chains of proteins. Specifically, we have developed NMR experiments for isolating the slow-relaxing ¹⁵N and ¹H components of NH₂ multiplets. Although even modest sensitivity gains in 2D NH₂-TROSY correlation maps compared to their decoupled NH₂–HSQC counterparts can be achieved only occasionally, substantial improvements in resolution of the NMR spectra are demonstrated for asparagine and glutamine NH₂ sites of a buried cavity mutant, L99A, of T4 lysozyme at 5 ºC. The NH₂-TROSY approach is applied to CPMG relaxation dispersion measurements at the side chain NH₂ positions of the L99A T4 lysozyme mutant — a model system for studies of the role of protein dynamics in ligand binding.