Dm. Lemaster, ASSESSMENT OF PROTEIN SOLUTION VERSUS CRYSTAL-STRUCTURE DETERMINATIONUSING SPIN-DIFFUSION-SUPPRESSED NOE AND HETERONUCLEAR RELAXATION DATA, Journal of biomolecular NMR, 9(1), 1997, pp. 79-93
A spin-diffusion-suppressed NOE buildup series has been measured for E
. coil thioredoxin. The extensive C-13 and N-15 relaxation data previo
usly reported for this protein allow for direct interpretation of dyna
mical contributions to the H-1-H-1 cross-relaxation rates for a large
proportion of the NOE cross peaks. Estimates of the average accuracy f
or these derived NOE distances are bounded by 4% and 10%, based on a c
omparison to the corresponding X-ray distances. An independent fluctua
tion model is proposed for prediction of the dynamical corrections to
H-1-H-1 cross-relaxation rates, based solely on experimental structura
l and heteronuclear relaxation data. This analysis is aided by the dem
onstration that heteronuclear order parameters greater than 0.6 depend
only on the variance of the H-X bond orientation, independent of the
motional model in either one- or two-dimensional diffusion (i.e., 1 -
S-2 = 3/4 sin(2) 2 theta(sigma)). The combination of spin-diffusion-su
ppressed NOE data and analysis of dynamical corrections to H-1-H-1 cro
ss-relaxation rates based on heteronuclear relaxation data has allowed
for a detailed interpretation of various discrepancies between the re
ported solution and crystal structures.