Excited flavin and pterin coenzyme molecules in evolution

Abstract

Excited flavin and pterin molecules are active in intermolecular energy transfer and in photocatalysis of redox reactions resulting in conservation of free energy. Flavin-containing pigments produced in models of the prebiotic environment are capable of converting photon energy into the energy of phosphoanhydride bonds of ATP. However, during evolution photochemical reactions involving excited FMN or FAD molecules failed to become participants of bioenergy transfer systems, but they appear in enzymes responsible for repair of UV-damaged DNA (DNA photolyases) and also in receptors of blue and UV-A light regulating vital functions of organisms. The families of these photoproteins (DNA-photolyases and cryptochromes, LOV-domain- and BLUF-domain-containing proteins) are different in the structure and in mechanisms of the photoprocesses. The excited flavin molecules are involved in photochemical processes in reaction centers of these photoproteins. In DNA photolyases and cryptochromes the excitation energy on the reaction center flavin is supplied from an antenna molecule that is bound with the same polypeptide. The role of antenna is played by MTHF or by 8-HDF in some DNA photolyases, i.e. also by molecules with known coenzyme functions in biocatalysis. Differences in the structure of chromophore-binding domains suggest an independent origin of the photoprotein families. The analysis of structure and properties of coenzyme molecules reveals some specific features that were significant in evolution for their being selected as chromophores in these proteins.

Fundamental molecules of life are pigments which arose and co-evolved as a response to the thermodynamic imperative of dissipating the prevailing solar spectrum

“…There is consistency in that they all absorb from 220 to 290 nm (except for histidine) and beyond 320 nm but not between 290 and 320 nm as would be expected if the atmospheric aldehydes were absorbing there (Sagan, 1973). Apart from their UV-C-UV-Babsorbing characteristics, pterin and flavin coenzymes are known to be photochemically active chromophores in a number of actual photoenzymes and sensory photoreceptor proteins (Kritsky et al, 1997(Kritsky et al, , 2010, suggesting a continuity of function since their first appearance near the origin of life. Examples are pterin-and flavin-based photoreceptor proteins called cryptochromes and phototropins in plants which mediate plant phototropism (Brautigam et al, 2004) and the pigment cyanopterin which functions as a UV/blue photoreceptor in cyanobacterial phototaxis (Moon et al, 2010).…”

The Evolution and Functional Role of Flavin‐based Prokaryotic Photoreceptors

“…Sq and hq can be protonated/deprotonated with pK a ‐values of ca. 8 and 6 . Also in LOV 450 , FMN or FAD in its noncovalently bound form is fully oxidized and referred to as “ ox ”.…”

Fromneontstofiliontsand their progenies...

“…Folates (precursors of tetrahydrofolate, THF) also participate in the biosynthesis of purine nucleotides. Without going into details of the biochemical paths [21], it is important to stress the metabolic relationship between all these compounds sensitive to light and that today participate to various extents in the biological oxydo-reduction reactions that produce energy.…”