Primary photochemistry of the dark- and light-adapted states of the YtvA protein from Bacillus subtilis
| Autor: | Klaas J. Hellingwerf, Robert Pullman, Dorte Madsen, Delmar S. Larsen, Sang-Hun Song, Lucy H. Freer, Jeroen B. van der Steen |
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| Přispěvatelé: | Molecular Microbial Physiology (SILS, FNWI) |
| Rok vydání: | 2013 |
| Předmět: | |
| Zdroj: | Biochemistry, 52(45), 7951-7963. American Chemical Society |
| ISSN: | 1520-4995 0006-2960 |
| Popis: | The primary (100 fs to 10 ns) and secondary (10 ns to 100 mus) photodynamics in the type II light-oxygen-voltage (LOV) domain from the blue light YtvA photoreceptor extracted from Bacillus subtilis were explored with transient absorption spectroscopy. The photodynamics of full-length YtvA were characterized after femtosecond 400 nm excitation of both the dark-adapted D447 state and the light-adapted S390 state. The S390 state relaxes on a 43 min time scale at room temperature back into D447, which is weakly accelerated by the introduction of imidazole. This is ascribed to an obstructed cavity in YtvA that hinders access to the embedded FMN chromophore and is more open in type I LOV domains. The primary photochemistry of dark-adapted YtvA is qualitatively similar to that of the type I LOV domains, including AsLOV2 from Avena sativa, but exhibits an appreciably higher (60% greater) terminal triplet yield, estimated near the maximal PhiISC value of approximately 78%; the other 22% decays via non-triplet-generating fluorescence. The subsequent secondary dynamics are inhomogeneous, with three triplet populations co-evolving: the faster-decaying (I)T* population (38% occupancy) with a 200 ns decay time is nonproductive in generating the S390 adduct state, a slower (II)T* population (57% occupancy) exhibits a high yield (Phiadduct approximately 100%) in generating S390 and a third (5%) (III)T*population persists (>100 mus) with unresolved photoactivity. The ultrafast photoswitching dynamics of the S390 state appreciably differ from those previously resolved for the type I AcLOV2 domain from Adiantum capillus-veneris [Kennis, J. T., et al. (2004) J. Am. Chem. Soc. 126, 4512], with a low-yield dissociation (Phidis approximately 2.5%) reaction, which is due to an ultrafast recombination reaction, following photodissociation, and is absent in AcLOV2, which results in the increased photoswitching activity of the latter domain. |
| Databáze: | OpenAIRE |
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