Mécanisme catalytique de la protochlorophyllide oxydoréductase : étude du couplage entre activité fonctionnelle et dynamique de la protéine

Abstract : Protochlorophyllide oxydoreductase (POR) catalyse the reduction of protochlorophyllide into chlorophyllide during the penultimate step of chlorophyll synthesis in green plants. The reaction is triggered by light and intermediates with different spectroscopic characteristics are formed. At low temperature each of these intermediates can be trapped to allow the study of the catalytic pathway.

We first demonstrate that the power and the wavelength of the light source initiating the reaction at low temperature influence the reaction. We highlight the existence of a pathway of reaction, alternative to the physiological one, driving to the formation of a non-functional product.

In a second part of the experimental work, both pathways the physiological and non-functional, have been followed by absorbance and fluorescence spectroscopy. These studies have been realized at temperatures between 100 and 293 K in solutions with different viscosity, in order to modify the temperature of glass transition (Tg). By following simultaneously Tg and the formation of the intermediates states we could show that the first steps of the physiological pathway were coupled with this transition, whereas those of the non-functional were independent. This work shows the existence of two different types of protein motions controlling the activity: large-scale protein motions, following the dielectric fluctuations in the bulk solvent and harmonic fluctuations of the protein, independent from the solvent. These studies have also direct important implications on how to design the correct protocol for kinetic crystallography experiments.
Complete list of metadatas

https://tel.archives-ouvertes.fr/tel-00011429
Contributor : Guillaume Durin <>
Submitted on : Thursday, January 19, 2006 - 6:57:41 PM
Last modification on : Friday, April 5, 2019 - 1:01:46 AM
Long-term archiving on: Saturday, April 3, 2010 - 7:48:30 PM

Identifiers

  • HAL Id : tel-00011429, version 1

Collections

Citation

Guillaume Durin. Mécanisme catalytique de la protochlorophyllide oxydoréductase : étude du couplage entre activité fonctionnelle et dynamique de la protéine. Biophysique [physics.bio-ph]. Université Joseph-Fourier - Grenoble I, 2005. Français. ⟨tel-00011429⟩

Share

Metrics

Record views

341

Files downloads

186