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Weak temperature dependence of P(+)H(A)(−) recombination in mutant Rhodobacter sphaeroides reaction centers

In contrast with findings on the wild-type Rhodobacter sphaeroides reaction center, biexponential P(+)H(A)(−) → PH(A) charge recombination is shown to be weakly dependent on temperature between 78 and 298 K in three variants with single amino acids exchanged in the vicinity of primary electron accep...

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Autores principales: Gibasiewicz, Krzysztof, Białek, Rafał, Pajzderska, Maria, Karolczak, Jerzy, Burdziński, Gotard, Jones, Michael R., Brettel, Klaus
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Springer Netherlands 2016
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4877430/
https://www.ncbi.nlm.nih.gov/pubmed/26942583
http://dx.doi.org/10.1007/s11120-016-0239-9
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author Gibasiewicz, Krzysztof
Białek, Rafał
Pajzderska, Maria
Karolczak, Jerzy
Burdziński, Gotard
Jones, Michael R.
Brettel, Klaus
author_facet Gibasiewicz, Krzysztof
Białek, Rafał
Pajzderska, Maria
Karolczak, Jerzy
Burdziński, Gotard
Jones, Michael R.
Brettel, Klaus
author_sort Gibasiewicz, Krzysztof
collection PubMed
description In contrast with findings on the wild-type Rhodobacter sphaeroides reaction center, biexponential P(+)H(A)(−) → PH(A) charge recombination is shown to be weakly dependent on temperature between 78 and 298 K in three variants with single amino acids exchanged in the vicinity of primary electron acceptors. These mutated reaction centers have diverse overall kinetics of charge recombination, spanning an average lifetime from ~2 to ~20 ns. Despite these differences a protein relaxation model applied previously to wild-type reaction centers was successfully used to relate the observed kinetics to the temporal evolution of the free energy level of the state P(+)H(A)(−) relative to P(+)B(A)(−). We conclude that the observed variety in the kinetics of charge recombination, together with their weak temperature dependence, is caused by a combination of factors that are each affected to a different extent by the point mutations in a particular mutant complex. These are as follows: (1) the initial free energy gap between the states P(+)B(A)(−) and P(+)H(A)(−), (2) the intrinsic rate of P(+)B(A)(−) → PB(A) charge recombination, and (3) the rate of protein relaxation in response to the appearance of the charge separated states. In the case of a mutant which displays rapid P(+)H(A)(−) recombination (ELL), most of this recombination occurs in an unrelaxed protein in which P(+)B(A)(−) and P(+)H(A)(−) are almost isoenergetic. In contrast, in a mutant in which P(+)H(A)(−) recombination is relatively slow (GML), most of the recombination occurs in a relaxed protein in which P(+)H(A)(−) is much lower in energy than P(+)H(A)(−). The weak temperature dependence in the ELL reaction center and a YLH mutant was modeled in two ways: (1) by assuming that the initial P(+)B(A)(−) and P(+)H(A)(−) states in an unrelaxed protein are isoenergetic, whereas the final free energy gap between these states following the protein relaxation is large (~250 meV or more), independent of temperature and (2) by assuming that the initial and final free energy gaps between P(+)B(A)(−) and P(+)H(A)(−) are moderate and temperature dependent. In the case of the GML mutant, it was concluded that the free energy gap between P(+)B(A)(−) and P(+)H(A)(−) is large at all times. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11120-016-0239-9) contains supplementary material, which is available to authorized users.
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spelling pubmed-48774302016-06-21 Weak temperature dependence of P(+)H(A)(−) recombination in mutant Rhodobacter sphaeroides reaction centers Gibasiewicz, Krzysztof Białek, Rafał Pajzderska, Maria Karolczak, Jerzy Burdziński, Gotard Jones, Michael R. Brettel, Klaus Photosynth Res Original Article In contrast with findings on the wild-type Rhodobacter sphaeroides reaction center, biexponential P(+)H(A)(−) → PH(A) charge recombination is shown to be weakly dependent on temperature between 78 and 298 K in three variants with single amino acids exchanged in the vicinity of primary electron acceptors. These mutated reaction centers have diverse overall kinetics of charge recombination, spanning an average lifetime from ~2 to ~20 ns. Despite these differences a protein relaxation model applied previously to wild-type reaction centers was successfully used to relate the observed kinetics to the temporal evolution of the free energy level of the state P(+)H(A)(−) relative to P(+)B(A)(−). We conclude that the observed variety in the kinetics of charge recombination, together with their weak temperature dependence, is caused by a combination of factors that are each affected to a different extent by the point mutations in a particular mutant complex. These are as follows: (1) the initial free energy gap between the states P(+)B(A)(−) and P(+)H(A)(−), (2) the intrinsic rate of P(+)B(A)(−) → PB(A) charge recombination, and (3) the rate of protein relaxation in response to the appearance of the charge separated states. In the case of a mutant which displays rapid P(+)H(A)(−) recombination (ELL), most of this recombination occurs in an unrelaxed protein in which P(+)B(A)(−) and P(+)H(A)(−) are almost isoenergetic. In contrast, in a mutant in which P(+)H(A)(−) recombination is relatively slow (GML), most of the recombination occurs in a relaxed protein in which P(+)H(A)(−) is much lower in energy than P(+)H(A)(−). The weak temperature dependence in the ELL reaction center and a YLH mutant was modeled in two ways: (1) by assuming that the initial P(+)B(A)(−) and P(+)H(A)(−) states in an unrelaxed protein are isoenergetic, whereas the final free energy gap between these states following the protein relaxation is large (~250 meV or more), independent of temperature and (2) by assuming that the initial and final free energy gaps between P(+)B(A)(−) and P(+)H(A)(−) are moderate and temperature dependent. In the case of the GML mutant, it was concluded that the free energy gap between P(+)B(A)(−) and P(+)H(A)(−) is large at all times. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11120-016-0239-9) contains supplementary material, which is available to authorized users. Springer Netherlands 2016-03-04 2016 /pmc/articles/PMC4877430/ /pubmed/26942583 http://dx.doi.org/10.1007/s11120-016-0239-9 Text en © The Author(s) 2016 Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
spellingShingle Original Article
Gibasiewicz, Krzysztof
Białek, Rafał
Pajzderska, Maria
Karolczak, Jerzy
Burdziński, Gotard
Jones, Michael R.
Brettel, Klaus
Weak temperature dependence of P(+)H(A)(−) recombination in mutant Rhodobacter sphaeroides reaction centers
title Weak temperature dependence of P(+)H(A)(−) recombination in mutant Rhodobacter sphaeroides reaction centers
title_full Weak temperature dependence of P(+)H(A)(−) recombination in mutant Rhodobacter sphaeroides reaction centers
title_fullStr Weak temperature dependence of P(+)H(A)(−) recombination in mutant Rhodobacter sphaeroides reaction centers
title_full_unstemmed Weak temperature dependence of P(+)H(A)(−) recombination in mutant Rhodobacter sphaeroides reaction centers
title_short Weak temperature dependence of P(+)H(A)(−) recombination in mutant Rhodobacter sphaeroides reaction centers
title_sort weak temperature dependence of p(+)h(a)(−) recombination in mutant rhodobacter sphaeroides reaction centers
topic Original Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4877430/
https://www.ncbi.nlm.nih.gov/pubmed/26942583
http://dx.doi.org/10.1007/s11120-016-0239-9
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