7r35
Difference-refined structure of fatty acid photodecarboxylase 300 ns following 400-nm laser irradiation of the dark-state determined by SFX
Structural highlights
FunctionFAP_CHLVA Catalyzes the decarboxylation of free fatty acids to n-alkanes or n-alkenes in response to blue light (PubMed:28860382, PubMed:30106504, PubMed:30673222). Substrate preference is toward fatty acids with C16 or C17 chains (PubMed:28860382, PubMed:30106504, PubMed:30673222). Saturated fatty acids are converted to alkanes, not alkenes (PubMed:28860382). The decarboxylation is initiated through electron abstraction from the fatty acid by the photo-excited FAD (PubMed:28860382).[1] [2] [3] Publication Abstract from PubMedUpon absorption of a blue-light photon, fatty-acid photodecarboxylase catalyzes the decarboxylation of free fatty acids to form hydrocarbons (for example alkanes or alkenes). The major components of the catalytic mechanism have recently been elucidated by combining static and time-resolved serial femtosecond crystallography (TR-SFX), time-resolved vibrational and electronic spectroscopies, quantum-chemical calculations and site-directed mutagenesis [Sorigue et al. (2021), Science, 372, eabd5687]. The TR-SFX experiments, which were carried out at four different picosecond to microsecond pump-probe delays, yielded input for the calculation of Fourier difference maps that demonstrated light-induced decarboxylation. Here, some of the difficulties encountered during the experiment as well as during data processing are highlighted, in particular regarding space-group assignment, a pump-laser power titration is described and data analysis is extended by structure-factor extrapolation of the TR-SFX data. Structure refinement against extrapolated structure factors reveals a reorientation of the generated hydrocarbon and the formation of a photoproduct close to Cys432 and Arg451. Identification of its chemical nature, CO2 or bicarbonate, was not possible because of the limited data quality, which was assigned to specificities of the crystalline system. Further TR-SFX experiments on a different crystal form are required to identify the photoproducts and their movements during the catalytic cycle. Time-resolved serial femtosecond crystallography on fatty-acid photodecarboxylase: lessons learned.,Hadjidemetriou K, Coquelle N, Barends TRM, De Zitter E, Schlichting I, Colletier JP, Weik M Acta Crystallogr D Struct Biol. 2022 Sep 1;78(Pt 9):1131-1142. doi:, 10.1107/S2059798322007525. Epub 2022 Aug 25. PMID:36048153[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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