Probing slow dynamics in high molecular weight proteins by methyl-TROSY NMR spectroscopy: Application to a 723-residue enzyme

A new CPMG-based multiple quantum relaxation dispersion experiment is presented for measuring millisecond dynamic processes at side-chain methyl positions in high molecular weight proteins. The experiment benefits from a methyl-TROSY effect in which cancellation of intramethyl dipole fields occurs, leading to methyl C-13-H-1 correlation spectra of high sensitivity and resolution (Tugarinov, V.; Hwang, P. M.; Ollerenshaw, J. E.; Kay, L. E. J. Am. Chem. Soc. 2003, 125, 10420-10428). The utility of the methodology is illustrated with an application to a highly deuterated, methyl-protonated sample of malate synthase G, an 82 kDa enzyme consisting of a single polypeptide chain. A comparison of the sensitivity obtained using the present approach relative to existing HSQC-type C-13 single quantum dispersion experiments shows a gain of a factor of 5.4 on average, significantly increasing the range of applications for this methodology.