Fatty acid photodecarboxylase (FAP) is a photoenzyme recently discovered and characterized by the coordinator and a partner of this proposal (Sorigué et al. 2017 Science 357:903). FAP catalyses the light-driven decarboxylation of fatty acids into hydrocarbons and CO2. It is only the third photoenzyme to be identified and thus represents a unique opportunity to deepen the understanding of light-driven catalysis. In spite of our initial characterization of FAP, 3D structures of intermediate-states and a detailed mechanistic understanding of FAP catalytic events have remained elusive. Our goal is to gain insight into the mechanistic events along the FAP photocycle, occurring from the ultra-fast time scale (femto- to picoseconds) right after photon absorption to product formation on slower time scales (nano- to milliseconds). Our central hypothesis is that photon absorption by FAD leads to product formation in FAP via a sequence of intermediate states within a photocycle that involves distinct spectroscopic and structural changes. Our objectives are the structural and spectroscopic characterization of FAD excited states on the ultra-fast time scale, the structure determination of catalytic intermediate states, the spectroscopic elucidation of electron and proton transfer steps, the structural and spectroscopic observation of the cleavage of the C-C bond leading to substrate decarboxylation, and the identification of a proton (or hydrogen atom) donor (amino acid or water molecule) whose existence has been postulated in the photocycle. The chosen methodology consists of a combination of experimental biophysical and biochemical techniques, including time-resolved crystallography at synchrotrons and X-ray free electron lasers (XFEL), FTIR and time-resolved infrared, absorption and fluorescence spectroscopy on FAP in solution and in crystals and complementary QM/MM computational methods. In particular, the project SNAPsHOTs will fully exploit the unique capabilities of the European facility for X-ray free electron laser (XFEL) that has been recently inaugurated and to which France contributed financially. Funding will be critical to maintain French leadership in a highly competitive field with potential industrial applications.
Ultimately, our project will provide a molecular movie of the FAP photocycle that features the structural changes occurring during light-driven enzyme catalysis at atomic resolution. Structural and mechanistic information should also be useful to improve stability, turnover or specificity of FAP in view of biotechnological applications.
Monsieur Frederic Beisson (Biologie végétale et microbiologie environnementales)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
IBS INSTITUT DE BIOLOGIE STRUCTURALE
BVME Biologie végétale et microbiologie environnementales
JOLIOT Institut des sciences du vivant FRÉDÉRIC-JOLIOT
CNRS - LOB Laboratoire d'optique et biosciences
Help of the ANR 514,677 euros
Beginning and duration of the scientific project: October 2018 - 36 Months