Manipulating the direction of electron transfer in the bacterial reaction center by swapping Phe for Tyr near BChl(M) (L181) and Tyr for Phe near BChl(L) (M208).
Biochemistry
; 40(40): 12132-9, 2001 Oct 09.
Article
em En
| MEDLINE
| ID: mdl-11580288
ABSTRACT
We have investigated the primary charge separation processes in Rb. capsulatus reaction centers (RCs) bearing the mutations Phe(L181) --> Tyr, Tyr(M208) --> Phe, and Leu(M212) --> His. In the YFH mutant, decay of the excited primary electron donor P occurs with an 11 +/- 2 ps time constant and is trifurcated to give (1) internal conversion to the ground state ( approximately 10% yield), (2) charge separation to the L side of the RC ( approximately 60% yield), and (3) electron transfer to the M-side bacteriopheophytin BPh(M) ( approximately 30% yield). These results relate previous work in which the ionizable residues Lys (at L178) and Asp (at M201) have been used to facilitate charge separation to the M side of the RC, and the widely studied L181 and M208 mutants. One conclusion that comes from this work is that the Tyr (M208) --> Phe and Gly(M201) --> Asp mutations near the L-side bacteriochlorophyll (BChl(L)) raise the free energy of P(+)BChl(L)(-) by comparable amounts. The results also suggest that the free energy of P(+)BChl(M)(-) is lowered more substantially by a Tyr at L181 than a Lys at L178. The results on the YFH mutant further demonstrate that the free energy differences between the L- and M-side charge-separated states play a significant role in the directionality of charge separation in the wild-type RC, and place limits on the contributing role of differential electronic matrix elements on the two sides of the RC.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Complexo de Proteínas do Centro de Reação Fotossintética
Idioma:
En
Revista:
Biochemistry
Ano de publicação:
2001
Tipo de documento:
Article
País de afiliação:
Estados Unidos