Trapped tyrosyl radical populations in modified reaction centers from Rhodobacter sphaeroides

A. J. Narváez, R. LoBrutto, James Paul Allen, J. C. Williams

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

The photosynthetic reaction center from the purple bacterium Rhodobacter sphaeroides has been modified such that the bacteriochlorophyll dimer, when it becomes oxidized after light excitation, is capable of oxidizing tyrosine residues. One factor in this ability is a high oxidation - reduction midpoint potential for the dimer, although the location and protein environment of the tyrosine residue appear to be critical as well. These factors were tested in a series of mutants, each of which contains changes, at residues L131, M160, M197, and M210, that give rise to a bacteriochlorophyll dimer with a midpoint potential of at least 800 mV. The protein environment was altered near tyrosine residues that are either present in the wild type or introduced by mutagenesis, focusing on residues that could act as acceptors for the phenolic proton of the tyrosine upon oxidation. These mutations include Ser M190 to His, which is near Tyr L162, the combination of His M193 to Tyr and Arg M164 to His, which adds a Tyr - His pair, and the combinations of Arg L135 to Tyr with Tyr L164 to His, Arg L135 to Tyr with Tyr L144 to Glu, and Arg L135 to Tyr with Tyr L164 to Phe. Radicals were produced in the mutants by using light to initiate electron transfer. The radicals were trapped by freezing the samples, and the relative populations of the oxidized dimer and tyrosyl radicals were determined by analysis of low-temperature electron paramagnetic resonance spectra. The mutants all showed evidence of tyrosyl radical formation at high pH, and the extent of radical formation at Tyr L135 with pH differed depending on the identity of L144 and L164. The results show that tyrosine residues within approximately 10 A° of the dimer can become oxidized when provided with a suitable protein environment.

Original languageEnglish
Pages (from-to)14379-14384
Number of pages6
JournalBiochemistry
Volume43
Issue number45
DOIs
Publication statusPublished - Nov 16 2004

Fingerprint

Rhodobacter sphaeroides
Dimers
Tyrosine
Bacteriochlorophylls
Population
Photosynthetic Reaction Center Complex Proteins
Light
Proteobacteria
Mutagenesis
Proteins
Electron Spin Resonance Spectroscopy
Freezing
Oxidation-Reduction
Paramagnetic resonance
Protons
Electrons
Oxidation
Mutation
Temperature

ASJC Scopus subject areas

  • Biochemistry

Cite this

Trapped tyrosyl radical populations in modified reaction centers from Rhodobacter sphaeroides. / Narváez, A. J.; LoBrutto, R.; Allen, James Paul; Williams, J. C.

In: Biochemistry, Vol. 43, No. 45, 16.11.2004, p. 14379-14384.

Research output: Contribution to journalArticle

Narváez, A. J. ; LoBrutto, R. ; Allen, James Paul ; Williams, J. C. / Trapped tyrosyl radical populations in modified reaction centers from Rhodobacter sphaeroides. In: Biochemistry. 2004 ; Vol. 43, No. 45. pp. 14379-14384.
@article{4bebd5ba4dec4f6989acbd30386b88da,
title = "Trapped tyrosyl radical populations in modified reaction centers from Rhodobacter sphaeroides",
abstract = "The photosynthetic reaction center from the purple bacterium Rhodobacter sphaeroides has been modified such that the bacteriochlorophyll dimer, when it becomes oxidized after light excitation, is capable of oxidizing tyrosine residues. One factor in this ability is a high oxidation - reduction midpoint potential for the dimer, although the location and protein environment of the tyrosine residue appear to be critical as well. These factors were tested in a series of mutants, each of which contains changes, at residues L131, M160, M197, and M210, that give rise to a bacteriochlorophyll dimer with a midpoint potential of at least 800 mV. The protein environment was altered near tyrosine residues that are either present in the wild type or introduced by mutagenesis, focusing on residues that could act as acceptors for the phenolic proton of the tyrosine upon oxidation. These mutations include Ser M190 to His, which is near Tyr L162, the combination of His M193 to Tyr and Arg M164 to His, which adds a Tyr - His pair, and the combinations of Arg L135 to Tyr with Tyr L164 to His, Arg L135 to Tyr with Tyr L144 to Glu, and Arg L135 to Tyr with Tyr L164 to Phe. Radicals were produced in the mutants by using light to initiate electron transfer. The radicals were trapped by freezing the samples, and the relative populations of the oxidized dimer and tyrosyl radicals were determined by analysis of low-temperature electron paramagnetic resonance spectra. The mutants all showed evidence of tyrosyl radical formation at high pH, and the extent of radical formation at Tyr L135 with pH differed depending on the identity of L144 and L164. The results show that tyrosine residues within approximately 10 A° of the dimer can become oxidized when provided with a suitable protein environment.",
author = "Narv{\'a}ez, {A. J.} and R. LoBrutto and Allen, {James Paul} and Williams, {J. C.}",
year = "2004",
month = "11",
day = "16",
doi = "10.1021/bi048691p",
language = "English",
volume = "43",
pages = "14379--14384",
journal = "Biochemistry",
issn = "0006-2960",
publisher = "American Chemical Society",
number = "45",

}

TY - JOUR

T1 - Trapped tyrosyl radical populations in modified reaction centers from Rhodobacter sphaeroides

AU - Narváez, A. J.

AU - LoBrutto, R.

AU - Allen, James Paul

AU - Williams, J. C.

PY - 2004/11/16

Y1 - 2004/11/16

N2 - The photosynthetic reaction center from the purple bacterium Rhodobacter sphaeroides has been modified such that the bacteriochlorophyll dimer, when it becomes oxidized after light excitation, is capable of oxidizing tyrosine residues. One factor in this ability is a high oxidation - reduction midpoint potential for the dimer, although the location and protein environment of the tyrosine residue appear to be critical as well. These factors were tested in a series of mutants, each of which contains changes, at residues L131, M160, M197, and M210, that give rise to a bacteriochlorophyll dimer with a midpoint potential of at least 800 mV. The protein environment was altered near tyrosine residues that are either present in the wild type or introduced by mutagenesis, focusing on residues that could act as acceptors for the phenolic proton of the tyrosine upon oxidation. These mutations include Ser M190 to His, which is near Tyr L162, the combination of His M193 to Tyr and Arg M164 to His, which adds a Tyr - His pair, and the combinations of Arg L135 to Tyr with Tyr L164 to His, Arg L135 to Tyr with Tyr L144 to Glu, and Arg L135 to Tyr with Tyr L164 to Phe. Radicals were produced in the mutants by using light to initiate electron transfer. The radicals were trapped by freezing the samples, and the relative populations of the oxidized dimer and tyrosyl radicals were determined by analysis of low-temperature electron paramagnetic resonance spectra. The mutants all showed evidence of tyrosyl radical formation at high pH, and the extent of radical formation at Tyr L135 with pH differed depending on the identity of L144 and L164. The results show that tyrosine residues within approximately 10 A° of the dimer can become oxidized when provided with a suitable protein environment.

AB - The photosynthetic reaction center from the purple bacterium Rhodobacter sphaeroides has been modified such that the bacteriochlorophyll dimer, when it becomes oxidized after light excitation, is capable of oxidizing tyrosine residues. One factor in this ability is a high oxidation - reduction midpoint potential for the dimer, although the location and protein environment of the tyrosine residue appear to be critical as well. These factors were tested in a series of mutants, each of which contains changes, at residues L131, M160, M197, and M210, that give rise to a bacteriochlorophyll dimer with a midpoint potential of at least 800 mV. The protein environment was altered near tyrosine residues that are either present in the wild type or introduced by mutagenesis, focusing on residues that could act as acceptors for the phenolic proton of the tyrosine upon oxidation. These mutations include Ser M190 to His, which is near Tyr L162, the combination of His M193 to Tyr and Arg M164 to His, which adds a Tyr - His pair, and the combinations of Arg L135 to Tyr with Tyr L164 to His, Arg L135 to Tyr with Tyr L144 to Glu, and Arg L135 to Tyr with Tyr L164 to Phe. Radicals were produced in the mutants by using light to initiate electron transfer. The radicals were trapped by freezing the samples, and the relative populations of the oxidized dimer and tyrosyl radicals were determined by analysis of low-temperature electron paramagnetic resonance spectra. The mutants all showed evidence of tyrosyl radical formation at high pH, and the extent of radical formation at Tyr L135 with pH differed depending on the identity of L144 and L164. The results show that tyrosine residues within approximately 10 A° of the dimer can become oxidized when provided with a suitable protein environment.

UR - http://www.scopus.com/inward/record.url?scp=4944261001&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=4944261001&partnerID=8YFLogxK

U2 - 10.1021/bi048691p

DO - 10.1021/bi048691p

M3 - Article

VL - 43

SP - 14379

EP - 14384

JO - Biochemistry

JF - Biochemistry

SN - 0006-2960

IS - 45

ER -