MUTANT AND WILD-TYPE MYOGLOBIN-CO PROTEIN DYNAMICS - VIBRATIONAL ECHOEXPERIMENTS

Citation
Kd. Rector et al., MUTANT AND WILD-TYPE MYOGLOBIN-CO PROTEIN DYNAMICS - VIBRATIONAL ECHOEXPERIMENTS, JOURNAL OF PHYSICAL CHEMISTRY B, 101(8), 1997, pp. 1468-1475
Citations number
48
Categorie Soggetti
Chemistry Physical
Journal title
JOURNAL OF PHYSICAL CHEMISTRY B
ISSN journal
15206106 → ACNP
Volume
101
Issue
8
Year of publication
1997
Pages
1468 - 1475
Database
ISI
SICI code
1089-5647(1997)101:8<1468:MAWMPD>2.0.ZU;2-K
Abstract
Picosecond infrared vibrational echo experiments on a mutant protein, H64V myoglobin-CO, are described and compared to experiments on wild-t ype myoglobin-CO. H64V is myoglobin with the distal histidine replaced by a valine. The vibrational dephasing experiments examine the influe nce of protein dynamics on the CO ligand, which is bound to the active site of the mutant protein, from low temperature to physiologically r elevant temperatures. The experiments were performed with a mid-infrar ed free electron laser tuned to the CO stretch mode at 1969 cm(-1). Th e vibrational echo results are combined with infrared pump-probe measu rements of the CO vibrational lifetime to yield the homogeneous pure d ephasing. The homogeneous pure dephasing is the Fourier transform of t he homogeneous line width with the lifetime contribution removed. The measurements were made from 60 to 300 K and show that the CO vibration al spectrum is inhomogeneously broadened at all temperatures studied. The mutant protein's CO vibrational pure dephasing rate is similar to 20% slower (narrower homogeneous pure dephasing line width) than the w ild-type protein at all temperatures, although the only difference bet ween the two proteins is the replacement of the wild-type's polar dist al histidine amino acid by a nonpolar valine. These results provide in sights into the mechanisms of the transmission of protein fluctuations to the CO ligand bound at the active site, and they are consistent wi th previously proposed mechanisms of protein-ligand coupling.