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Microsecond Protein Dynamics Measured by 13 C α Rotating‐Frame Spin Relaxation
Author(s) -
Lundström Patrik,
Akke Mikael
Publication year - 2005
Publication title -
chembiochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.05
H-Index - 126
eISSN - 1439-7633
pISSN - 1439-4227
DOI - 10.1002/cbic.200500086
Subject(s) - microsecond , relaxation (psychology) , chemistry , protein dynamics , dihedral angle , molecular dynamics , crystallography , chemical physics , nuclear magnetic resonance , analytical chemistry (journal) , physics , computational chemistry , molecule , psychology , social psychology , hydrogen bond , organic chemistry , chromatography , astronomy
NMR spin relaxation in the rotating frame ( R 1 ρ ) is a unique method for atomic‐resolution characterization of conformational (chemical) exchange processes occurring on the microsecond timescale. We present a rotating‐frame 13 C α relaxation dispersion experiment for measuring conformational dynamics in uniformly 13 C‐labeled proteins. The experiment was validated by using the E140Q mutant of the C‐terminal fragment of calmodulin, which exhibits significant conformational exchange between two major conformations, as gauged from previous 15 N and 1 H relaxation studies. Consistent with previous work, the present 13 C α R 1 ρ experiment detects conformational‐exchange dynamics throughout the protein. The average correlation time of 〈 τ ex 〉=25±8 μs is in excellent agreement with those determined previously from 1 H and 15 N R 1ρ relaxation data: 〈 τ ex 〉=19±7 and 21±3 μs, respectively. The extracted chemical‐shift differences between the exchanging states reveal significant fluctuations in dihedral angles within single regions of Ramachandran φ – ψ space, that were not identified from the 1 H and 15 N relaxation data. The present results underscore the advantage of using several types of nuclei to probe exchange dynamics in biomolecules.