Phot photoreceptors make up an important protein family regulating biological processes in response to blue light. They contain two light, @entity26 , and voltage sensitive (LOV) domains and a @entity563 / @entity1889 kinase domain. Both LOV domains noncovalently bind a @entity10698 (FMN). Upon absorption of blue light, the LOV domains undergo a photocycle, transiently forming a covalent adduct of a @entity462 residue and the FMN (LOV-390). The mechanism of formation of this @entity1785 - @entity1432 adduct is still unclear. We studied a mutant of the LOV1 domain from the green alga @entity2060 with a @entity1853 replacing the reactive @entity462 57 (C57M). As in the wild type, irradiation leads to formation of a photoadduct, which, however, is irreversibly converted into a red absorbing species, C57M-675. On the basis of spectroscopic results and the 2.1 A resolution crystal structure, this highly unusual @entity10698 species was assigned to a neutral @entity1785 radical covalently attached to the apoprotein at the N(5) position. In contrast to other flavoprotein neutral radicals, C57M-675 is stable even under aerobic or denaturing conditions. Pathways for the photoinduced formation of the adduct are discussed for the C57M mutant as well as the wild-type LOV1 domain.

Irreversible photoreduction of XXXX in a mutated Phot-LOV1 domain.

@entity462 :: ('MESH:D003545', 'Chemical') :: ['cysteine'] @entity1785 :: ('MESH:C024132', 'Chemical') :: ['flavin'] @entity26 :: ('MESH:D010100', 'Chemical') :: ['oxygen'] @entity10698 :: ('MESH:D005486', 'Chemical') :: ['flavin mononucleotide', 'FMN'] @entity1853 :: ('MESH:D008715', 'Chemical') :: ['methionine'] @entity1432 :: ('CHEBI:29256', 'Chemical') :: ['thiol'] @entity563 :: ('CHEBI:17822', 'Chemical') :: ['serine'] @entity1889 :: ('CHEBI:26986', 'Chemical') :: ['threonine'] @entity2060 :: ('3055', 'Species') :: ['Chlamydomonas reinhardtii']
@entity1785 :: (MESH:C024132,Chemical) :: ['flavin']
