Direct and mediated electron transfer between intact succinate:quinone oxidoreductase from Bacillus subtilis and a surface modified gold electrode reveals redox state-dependent conformational changes.
(2008) In Biochimica et Biophysica Acta - Bioenergetics 1777(9). p.1203-1210- Abstract
- Succinate:quinone oxidoreductase (SQR) from Bacillus subtilis consists of two hydrophilic protein subunits comprising succinate dehydrogenase, and a di-heme membrane anchor protein harboring two putative quinone binding sites, Q(p) and Q(d). In this work we have used spectroelectrochemistry to study the electronic communication between purified SQR and a surface modified gold capillary electrode. In the presence of two soluble quinone mediators the midpoint potentials of both hemes were revealed essentially as previously determined by conventional redox titration (heme b(H), E(m)=+65 mV, heme b(L), E(m)=-95 mV). In the absence of mediators the enzyme still communicated with the electrode, albeit with a reproducible hysteresis, resulting in... (More)
- Succinate:quinone oxidoreductase (SQR) from Bacillus subtilis consists of two hydrophilic protein subunits comprising succinate dehydrogenase, and a di-heme membrane anchor protein harboring two putative quinone binding sites, Q(p) and Q(d). In this work we have used spectroelectrochemistry to study the electronic communication between purified SQR and a surface modified gold capillary electrode. In the presence of two soluble quinone mediators the midpoint potentials of both hemes were revealed essentially as previously determined by conventional redox titration (heme b(H), E(m)=+65 mV, heme b(L), E(m)=-95 mV). In the absence of mediators the enzyme still communicated with the electrode, albeit with a reproducible hysteresis, resulting in the reduction of both hemes occurring approximately at the midpoint potential of heme b(L), and with a pronounced delay of reoxidation. When the specific inhibitor 2-n-heptyl-4 hydroxyquinoline N-oxide (HQNO), which binds to Q(d) in B. subtilis SQR, was added together with the two quinone mediators, rapid reductive titration was still possible which can be envisioned as an electron transfer occurring via the HQNO insensitive Q(p) site. In contrast, the subsequent oxidative titration was severely hampered in the presence of HQNO, in fact it completely resembled the unmediated reaction. If mediators communicate with Q(p) or Q(d), either event is followed by very rapid electron redistribution within the enzyme. Taken together, this strongly suggests that the accessibility of Q(p) depended on the redox state of the hemes. When both hemes were reduced, and Q(d) was blocked by HQNO, quinone-mediated communication via the Q(p) site was no longer possible, revealing a redox-dependent conformational change in the membrane anchor domain. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/1181585
- author
- Christenson, Andreas LU ; Gustavsson, Tobias LU ; Gorton, Lo LU and Hägerhäll, Cecilia LU
- organization
- publishing date
- 2008
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Mercaptohexanol, Spectroelectrochemistry, Quinone, QFR, SdhC, Cytochrome b, SQR, Gold capillary
- in
- Biochimica et Biophysica Acta - Bioenergetics
- volume
- 1777
- issue
- 9
- pages
- 1203 - 1210
- publisher
- Elsevier
- external identifiers
-
- wos:000259287200015
- pmid:18598669
- scopus:50949128131
- pmid:18598669
- ISSN
- 0005-2728
- DOI
- 10.1016/j.bbabio.2008.05.450
- language
- English
- LU publication?
- yes
- additional info
- The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Biochemistry and Structural Biology (S) (000006142), Analytical Chemistry (S/LTH) (011001004)
- id
- 1e94252c-e444-4fcb-8d1b-4dd52ff0bb7c (old id 1181585)
- date added to LUP
- 2016-04-01 13:33:08
- date last changed
- 2022-03-14 00:36:22
@article{1e94252c-e444-4fcb-8d1b-4dd52ff0bb7c,
abstract = {{Succinate:quinone oxidoreductase (SQR) from Bacillus subtilis consists of two hydrophilic protein subunits comprising succinate dehydrogenase, and a di-heme membrane anchor protein harboring two putative quinone binding sites, Q(p) and Q(d). In this work we have used spectroelectrochemistry to study the electronic communication between purified SQR and a surface modified gold capillary electrode. In the presence of two soluble quinone mediators the midpoint potentials of both hemes were revealed essentially as previously determined by conventional redox titration (heme b(H), E(m)=+65 mV, heme b(L), E(m)=-95 mV). In the absence of mediators the enzyme still communicated with the electrode, albeit with a reproducible hysteresis, resulting in the reduction of both hemes occurring approximately at the midpoint potential of heme b(L), and with a pronounced delay of reoxidation. When the specific inhibitor 2-n-heptyl-4 hydroxyquinoline N-oxide (HQNO), which binds to Q(d) in B. subtilis SQR, was added together with the two quinone mediators, rapid reductive titration was still possible which can be envisioned as an electron transfer occurring via the HQNO insensitive Q(p) site. In contrast, the subsequent oxidative titration was severely hampered in the presence of HQNO, in fact it completely resembled the unmediated reaction. If mediators communicate with Q(p) or Q(d), either event is followed by very rapid electron redistribution within the enzyme. Taken together, this strongly suggests that the accessibility of Q(p) depended on the redox state of the hemes. When both hemes were reduced, and Q(d) was blocked by HQNO, quinone-mediated communication via the Q(p) site was no longer possible, revealing a redox-dependent conformational change in the membrane anchor domain.}},
author = {{Christenson, Andreas and Gustavsson, Tobias and Gorton, Lo and Hägerhäll, Cecilia}},
issn = {{0005-2728}},
keywords = {{Mercaptohexanol; Spectroelectrochemistry; Quinone; QFR; SdhC; Cytochrome b; SQR; Gold capillary}},
language = {{eng}},
number = {{9}},
pages = {{1203--1210}},
publisher = {{Elsevier}},
series = {{Biochimica et Biophysica Acta - Bioenergetics}},
title = {{Direct and mediated electron transfer between intact succinate:quinone oxidoreductase from Bacillus subtilis and a surface modified gold electrode reveals redox state-dependent conformational changes.}},
url = {{http://dx.doi.org/10.1016/j.bbabio.2008.05.450}},
doi = {{10.1016/j.bbabio.2008.05.450}},
volume = {{1777}},
year = {{2008}},
}