1. Proc Natl Acad Sci U S A. 2006 Aug 8;103(32):11910-5. Epub 2006 Jul 31.

Complementarity of ensemble and single-molecule measures of protein motion: a
relaxation dispersion NMR study of an enzyme complex.

Vallurupalli P, Kay LE.

Department of Medical Genetics, University of Toronto, Toronto, ON, Canada M5S
1A8.

Single-molecule fluorescence experiments have shown that the conformation of the 
complex between Escherichia coli general NAD(P)H:flavin oxidoreductase (FRE) and 
flavin adenine dinucleotide (FAD) fluctuates over a range of timescales between
10(-4) and 1 s. Here we use (15)N and (13)C relaxation dispersion NMR methods to 
study millisecond-timescale dynamics in the complex. In this time regime, the
protein is extremely flexible, with residues that undergo conformational exchange
located throughout the molecule. Three distinct regions of dynamics are
quantified, with two of them involving residues making contact to the donor
(Tyr-35) and acceptor (FAD) sites that participate in the electron transfer
reaction monitored in single-molecule experiments. Modulation of the
donor-acceptor distance through these conformational exchange processes,
occurring with rates of approximately 400 and 1,200 s(-1) (22 degrees C), affects
the rate of electron transfer and partially accounts for the range of the
observed dynamics monitored in the fluorescence experiments.

PMCID: PMC1567672
PMID: 16880391 [PubMed - indexed for MEDLINE]