Luciferase & LuxF

 

The emission of light by biological species (bioluminescence) is a fascinating process found in diverse organisms such as bacteria, fungi, insects, fish, limpets and nematodes. In all cases the bioluminescent process is based on a chemiluminescent reaction in which the chemical energy is (partially) transformed into light energy ("cold light"). All bioluminescent processes require a luciferase, i.e. an enzyme catalyzing the chemiluminescent reaction, and a luciferin, which can be considered a coenzyme. During the bioluminescent reaction the luciferin is generated in an excited state and serves as the emitter of light energy. In our laboratory, we are interested in the bioluminescence of marine photobacteria. In these bacteria, luciferase is composed of an alpha/beta-heterodimeric protein, which binds reduced flavinmononucleotide (FMN) as the luciferin. The reduced FMN reacts with molecular dioxygen to a hydroperoxide intermediate with subsequent oxidation of a long-chain fatty aldehyde (e.g. tetradecanal) to the corresponding fatty acid (e.g. myristic acid). During this oxidation process, an excited flavin intermediate is generated which emits light. Some marine photobacteria possess an additional protein called LuxF which was found in complex with a myristylated flavin derivative where the C-3 atom of myristic acid is covalently attached to the 6-position of the flavin ring system. It was postulated that this flavin adduct is generated in the luciferase catalyzed bioluminescent reaction. Furthermore, it was speculated that LuxF sequesters the myristylated flavin adduct in order to prevent inhibition of the bioluminescent reaction. However, both hypotheses have not been tested on a biochemical or physiological level yet. Hence, in this study we will design and perform experiments to examine the putative generation of myristylated FMN through the luciferase reaction (thesis project of Thomas Bergner).


Structure of a LuxF dimer in the absence (red) and presence (blue) of the myristylated flavin derivative (pdb code 1NFP)