Rm. Losel et al., ASYMMETRY OF CATALYTIC BUT NOT OF NONCATALYTIC SITES ON ESCHERICHIA-COLI F1-ATPASE IN SOLUTION AS OBSERVED USING ELECTRON-SPIN-RESONANCE SPECTROSCOPY, Biochemistry, 36(6), 1997, pp. 1188-1193
We have employed electron spin resonance (ESR) spectroscopy using diff
erent spin-labeled nucleotides to probe the environment of nucleotides
bound at catalytic and noncatalytic nucleotide binding sites of the E
scherichia coli F-1-ATPase. We found that nucleotides bound in the non
catalytic binding sites were strongly immobilized and resulted in ESR
spectra with one single corresponding spectral component. Nucleotide b
ound at the catalytic binding sites gave rise to two different signals
in the ESR spectra indicative of two distinct conformations of the ca
talytic sites of the protein. One conformation of the catalytic sites
is very tight, resulting in signals identical to those of the noncatal
ytic sites, while the second type of catalytic sites permitted an unus
ually high mobility of the bound spin-labeled nucleotide. The findings
are compared to the requirements of the binding change mechanism and
to the features of the nucleotide binding sites as elucidated from the
X-ray structural model of the beef heart mitochondrial enzyme.