Photochemical characterization of actinorhodopsin and its functional existence in the natural host.
Biochim Biophys Acta
; 1857(12): 1900-1908, 2016 12.
Article
en En
| MEDLINE
| ID: mdl-27659506
ABSTRACT
Actinorhodopsin (ActR) is a light-driven outward H+ pump. Although the genes of ActRs are widely spread among freshwater bacterioplankton, there are no prior data on their functional expression in native cell membranes. Here, we demonstrate ActR phototrophy in the native actinobacterium. Genome analysis showed that Candidatus Rhodoluna planktonica, a freshwater actinobacterium, encodes one microbial rhodopsin (RpActR) belonging to the ActR family. Reflecting the functional expression of RpActR, illumination induced the acidification of the actinobacterial cell suspension and then elevated the ATP content inside the cells. The photochemistry of RpActR was also examined using heterologously expressed RpActR in Escherichia coli membranes. The purified RpActR showed λmax at 534nm and underwent a photocycle characterized by the very fast formation of M intermediate. The subsequent intermediate, named P620, could be assigned to the O intermediate in other H+ pumps. In contrast to conventional O, the accumulation of P620 remains prominent, even at high pH. Flash-induced absorbance changes suggested that there exists only one kind of photocycle at any pH. However, above pH7, RpActR shows heterogeneity in the H+ transfer sequences one first captures H+ and then releases it during the formation and decay of P620, while the other first releases H+ prior to H+ uptake during P620 formation.
Palabras clave
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Contexto en salud:
3_ND
Problema de salud:
3_neglected_diseases
/
3_zoonosis
Asunto principal:
Adenosina Trifosfato
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Actinobacteria
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Rodopsinas Microbianas
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Metabolismo Energético
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Procesos Fototróficos
/
Luz
Idioma:
En
Revista:
Biochim Biophys Acta
Año:
2016
Tipo del documento:
Article
País de afiliación:
Japón