Spectroscopic characterization of flavin mononucleotide bound to the LOV1 domain of Phot1 from Chlamydomonas reinhardtii.
Photochem Photobiol
; 75(5): 479-87, 2002 May.
Article
em En
| MEDLINE
| ID: mdl-12017473
ABSTRACT
The absorption and emission behavior of flavin mononucleotide (FMN) in the light-, oxygen- and voltage-sensitive (LOV) domain LOV1 of the photoreceptor Phot1 from the green alga Chlamydomonas reinhardtii was studied. The results from the wild-type (LOV1-WT) were compared with those from a mutant in which cysteine 57 was replaced by serine (LOV1-C57S), and with free FMN in aqueous solution. A fluorescence quantum yield of phi(F) = 0.30 and a fluorescence lifetime of tau(F) = 4.6 ns were determined for FMN in the mutant LOV1-C57S, whereas these quantities are reduced to about phi(F) = 0.17 and tau(F) = 2.9 ns for LOV1-WT, indicating an enhanced intersystem crossing in LOV1-WT because of the adjacent sulfur of C57. A single-exponential fluorescence decay was observed in picosecond laser time-resolved fluorescence measurements for both LOV1-WT and LOV1-C57S as expected for excited singlet state relaxation by intersystem crossing and internal conversion. An excitation intensity dependent fluorescence signal saturation was observed in steady-state fluorescence measurements for LOV1-WT, which is thought to be because of the formation of a long-lived intermediate flavin-C(4a)-cysteinyl adduct in the triplet state (few microseconds triplet lifetime, adduct lifetime around 150 s). No photobleaching was observed for LOV1-C57S, because no thiol group is present in the vicinity of FMN for an adduct formation.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Fosfoproteínas
/
Chlamydomonas reinhardtii
/
Mononucleotídeo de Flavina
Limite:
Animals
Idioma:
En
Revista:
Photochem Photobiol
Ano de publicação:
2002
Tipo de documento:
Article
País de afiliação:
Alemanha