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Title: A Cu{sup 2+} site common to photosynthetic bacterial reaction centers from Rb. sphaeroides, Rb. capsulatus, and Rps. viridis.

Abstract

The interaction of metal ions with isolated photosynthetic reaction centers (RCs) from the purple bacteria Rhodobacter sphaeroides, Rhodobacter capsulatus, and Rhodopseudomonas viridis has been investigated with transient optical and magnetic resonance techniques. In RCs from all species, the electrochromic response of the bacteriopheophytin cofactors associated with Q{sub A}{sup -}Q{sub B} {yields} Q{sub A}Q{sub B}{sup -} electron transfer is slowed in the presence of Cu{sup 2+}. This slowing is similar to the metal ion effect observed for RCs from Rb. sphaeroides where Zn{sup 2+} was bound to a specific site on the surface of the RC [Utschig et al. (1998) Biochemistry 37, 8278]. The coordination environments of the Cu{sup 2+} sites were probed with electron paramagnetic resonance (EPR) spectroscopy, providing the first direct spectroscopic evidence for the existence of a second metal site in RCs from Rb. capsulatus and Rps. viridis. In the dark, RCs with Cu{sup 2+} bound to the surface exhibit axially symmetric EPR spectra. Electron spin echo envelope modulation (ESEEM) spectral results indicate multiple weakly hyperfine coupled {sup 14}N nuclei in close proximity to Cu{sup 2+}. These ESEEM spectra resemble those observed for Cu{sup 2+} RCs from Rb. sphaeroides [Utschig et al. (2000) Biochemistry 39, 2961] and indicatemore » that two or more histidines ligate the Cu{sup 2+} at the surface site in each RC. Thus, RCs from Rb. sphaeroides, Rb. capsulatus, and Rps. viridis each have a structurally analogous Cu{sup 2+} binding site that is involved in modulating the Q{sub A}{sup -}Q{sub B} {yields} Q{sub A}Q{sub B}{sup -} electron-transfer process. Inspection of the Rps. viridis crystal structure reveals four potential histidine ligands from three different subunits (M16, H178, H72, and L211) located beneath the Q{sub B} binding pocket. The location of these histidines is surprisingly similar to the grouping of four histidine residues (H68, H126, H128, and L211) observed in the Rb. sphaeroides RC crystal structure. Further elucidation of these Cu{sup 2+} sites will provide a means to investigate localized proton entry into the RCs of Rb. capsulatus and Rps. viridis as well as locate a site of protein motions coupled with electron transfer.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
943201
Report Number(s):
ANL/CHM/JA-38225
TRN: US200916%%649
DOE Contract Number:  
DE-AC02-06CH11357
Resource Type:
Journal Article
Journal Name:
Biochemistry
Additional Journal Information:
Journal Volume: 40; Journal Issue: 20 ; May 22, 2001
Country of Publication:
United States
Language:
ENGLISH
Subject:
36 MATERIALS SCIENCE; CRYSTAL STRUCTURE; ELECTRON SPIN RESONANCE; ELECTRON TRANSFER; HEAVY METALS; MAGNETIC RESONANCE; PHOTOSYNTHETIC BACTERIA; PHOTOSYNTHETIC REACTION CENTERS; RHODOPSEUDOMONAS

Citation Formats

Utschig, L M, Poluektov, O, Schlesselman, S L, Thurnauer, M C, Tiede, D M, and Chemistry. A Cu{sup 2+} site common to photosynthetic bacterial reaction centers from Rb. sphaeroides, Rb. capsulatus, and Rps. viridis.. United States: N. p., 2001. Web. doi:10.1021/bi0029191.
Utschig, L M, Poluektov, O, Schlesselman, S L, Thurnauer, M C, Tiede, D M, & Chemistry. A Cu{sup 2+} site common to photosynthetic bacterial reaction centers from Rb. sphaeroides, Rb. capsulatus, and Rps. viridis.. United States. https://doi.org/10.1021/bi0029191
Utschig, L M, Poluektov, O, Schlesselman, S L, Thurnauer, M C, Tiede, D M, and Chemistry. Tue . "A Cu{sup 2+} site common to photosynthetic bacterial reaction centers from Rb. sphaeroides, Rb. capsulatus, and Rps. viridis.". United States. https://doi.org/10.1021/bi0029191.
@article{osti_943201,
title = {A Cu{sup 2+} site common to photosynthetic bacterial reaction centers from Rb. sphaeroides, Rb. capsulatus, and Rps. viridis.},
author = {Utschig, L M and Poluektov, O and Schlesselman, S L and Thurnauer, M C and Tiede, D M and Chemistry},
abstractNote = {The interaction of metal ions with isolated photosynthetic reaction centers (RCs) from the purple bacteria Rhodobacter sphaeroides, Rhodobacter capsulatus, and Rhodopseudomonas viridis has been investigated with transient optical and magnetic resonance techniques. In RCs from all species, the electrochromic response of the bacteriopheophytin cofactors associated with Q{sub A}{sup -}Q{sub B} {yields} Q{sub A}Q{sub B}{sup -} electron transfer is slowed in the presence of Cu{sup 2+}. This slowing is similar to the metal ion effect observed for RCs from Rb. sphaeroides where Zn{sup 2+} was bound to a specific site on the surface of the RC [Utschig et al. (1998) Biochemistry 37, 8278]. The coordination environments of the Cu{sup 2+} sites were probed with electron paramagnetic resonance (EPR) spectroscopy, providing the first direct spectroscopic evidence for the existence of a second metal site in RCs from Rb. capsulatus and Rps. viridis. In the dark, RCs with Cu{sup 2+} bound to the surface exhibit axially symmetric EPR spectra. Electron spin echo envelope modulation (ESEEM) spectral results indicate multiple weakly hyperfine coupled {sup 14}N nuclei in close proximity to Cu{sup 2+}. These ESEEM spectra resemble those observed for Cu{sup 2+} RCs from Rb. sphaeroides [Utschig et al. (2000) Biochemistry 39, 2961] and indicate that two or more histidines ligate the Cu{sup 2+} at the surface site in each RC. Thus, RCs from Rb. sphaeroides, Rb. capsulatus, and Rps. viridis each have a structurally analogous Cu{sup 2+} binding site that is involved in modulating the Q{sub A}{sup -}Q{sub B} {yields} Q{sub A}Q{sub B}{sup -} electron-transfer process. Inspection of the Rps. viridis crystal structure reveals four potential histidine ligands from three different subunits (M16, H178, H72, and L211) located beneath the Q{sub B} binding pocket. The location of these histidines is surprisingly similar to the grouping of four histidine residues (H68, H126, H128, and L211) observed in the Rb. sphaeroides RC crystal structure. Further elucidation of these Cu{sup 2+} sites will provide a means to investigate localized proton entry into the RCs of Rb. capsulatus and Rps. viridis as well as locate a site of protein motions coupled with electron transfer.},
doi = {10.1021/bi0029191},
url = {https://www.osti.gov/biblio/943201}, journal = {Biochemistry},
number = 20 ; May 22, 2001,
volume = 40,
place = {United States},
year = {2001},
month = {5}
}