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Correlation of proton release and electrochromic shifts of the optical spectrum due to oxidation of tyrosine in reaction centers from Rhodobacter sphaeroides.
Kálmán, L; LoBrutto, R; Narváez, A J; Williams, J C; Allen, J P.
Afiliación
  • Kálmán L; Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287, USA.
Biochemistry ; 42(45): 13280-6, 2003 Nov 18.
Article en En | MEDLINE | ID: mdl-14609339
Reaction centers from the Y(L167) mutant of Rhodobacter sphaeroides, containing a highly oxidizing bacteriochlorophyll dimer and a tyrosine residue substituted at Phe L167, were compared to reaction centers from the Y(M) mutant, with a tyrosine at M164, and a quadruple mutant containing a highly oxidizing dimer but no nearby tyrosine residue. Distinctive features in the light-induced optical and EPR spectra showed that the oxidized bacteriochlorophyll dimer was reduced by Tyr L167 in the Y(L167) mutant, resulting in a tyrosyl radical, as has been found for Tyr M164 in the Y(M) mutant. In the Y(L167) mutant, the net proton uptake after formation of the tyrosyl radical and the reduced primary quinone ranged from +0.1 to +0.3 H(+)/reaction center between pH 6 and pH 10, with a dependence that is similar to the quadruple mutant but different than the large proton release observed in the Y(M) mutant. In the light-induced absorption spectrum in the 700-1000 nm region, the Y(L167) mutant exhibited unique changes that can be assigned as arising primarily from an approximately 30 nm blue shift of the dimer absorption band. The optical signals in the Y(L167) mutant were pH dependent, with a pK(a) value of approximately 8.7, indicating that the tyrosyl radical is stabilized at high pH. The results are modeled by assuming that the phenolic proton of Tyr L167 is trapped in the protein after oxidation of the tyrosine, resulting in electrostatic interactions with the tetrapyrroles and nearby residues.
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Colección: 01-internacional Base de datos: MEDLINE Asunto principal: Protones / Tirosina / Rhodobacter sphaeroides / Proteínas del Complejo del Centro de Reacción Fotosintética Idioma: En Revista: Biochemistry Año: 2003 Tipo del documento: Article País de afiliación: Estados Unidos Pais de publicación: Estados Unidos
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Colección: 01-internacional Base de datos: MEDLINE Asunto principal: Protones / Tirosina / Rhodobacter sphaeroides / Proteínas del Complejo del Centro de Reacción Fotosintética Idioma: En Revista: Biochemistry Año: 2003 Tipo del documento: Article País de afiliación: Estados Unidos Pais de publicación: Estados Unidos