Effects of Asp residues near the L-side pigments in bacterial reaction centers

Biochemistry
B A HellerC Kirmaier

Abstract

The primary photochemistry in Rhodobacter capsulatus reaction centers (RCs) containing the Phe to Asp mutation at L polypeptide residue 121 near the photoactive bacteriopheophytin (BPhL) is characterized using ultrafast transient absorption spectroscopy. At 285 K, initial charge separation from P* proceeds with essentially unity quantum yield in approximately 6 ps to form a transient denoted P+I-. This transient is proposed to involve P+BPhL- and probably P+BChlL- as well (BChlL is the L-side bacteriochlorophyll molecule). P+I- decays in approximately 150 ps both by electron transfer to give P+QA- (approximately 78% yield) and by charge recombination to the ground state (approximately 22% yield). These results indicate that the F(L121)D mutant is closely related, in terms of its electron transfer properties, to previously reported RCs in which BPhL is replaced with a bacteriochlorophyll (beta-type RCs) or a pheophytin. However, the native BPhL pigment is retained in the F(L121)D mutant. We propose that the Asp at L121 raises the free energy of P+BPhL-, thereby giving rise to the altered photochemistry. At 77 K, the P+I- lifetime is shortened slightly to approximately 120 ps and the yield of P+QA- is increased to approximately 8...Continue Reading

References

Mar 1, 1989·The Biochemical Journal·C T Zimmerle, C Frieden
Aug 1, 1983·Proceedings of the National Academy of Sciences of the United States of America·J Eccles, B Honig
Sep 1, 1987·Photosynthesis Research·C Kirmaier, D Holten

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Citations

Mar 8, 2011·The European Physical Journal. E, Soft Matter·M Pudlak, R Pincak
Dec 15, 2015·Biochimica Et Biophysica Acta·Kaitlyn M FariesChristine Kirmaier
Aug 6, 2014·Biochimica Et Biophysica Acta·Lucas KresselChristine Kirmaier
Dec 7, 2014·Photosynthesis Research·Tatiana Y FufinaVladimir A Shuvalov
Jul 1, 2020·Proceedings of the National Academy of Sciences of the United States of America·Hiroyuki TamuraHiroshi Ishikita
Jan 10, 2009·The Journal of Physical Chemistry. B·Christine Kirmaier, Dewey Holten
Jul 3, 2021·Photochemical & Photobiological Sciences : Official Journal of the European Photochemistry Association and the European Society for Photobiology·Krzysztof GibasiewiczMichael R Jones

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