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Biological Chemistry

Editor-in-Chief: Brüne, Bernhard

Editorial Board: Buchner, Johannes / Lei, Ming / Ludwig, Stephan / Thomas, Douglas D. / Turk, Boris / Wittinghofer, Alfred


IMPACT FACTOR 2018: 3.014
5-year IMPACT FACTOR: 3.162

CiteScore 2018: 3.09

SCImago Journal Rank (SJR) 2018: 1.482
Source Normalized Impact per Paper (SNIP) 2018: 0.820

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1437-4315
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Volume 392, Issue 10

Issues

Conformational changes of the chaperone SecB upon binding to a model substrate – bovine pancreatic trypsin inhibitor (BPTI)

Michaela M. Haimann
  • Fachbereich Chemie/Abteilung Biochemie der Technischen Universität Kaiserslautern, Erwin Schrödinger Str. 54, D-67663 Kaiserslautern, Germany
  • Other articles by this author:
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/ Yasar Akdogan
  • Polymer-Spektroskopie, Max-Planck-Institut für Polymerforschung, Ackermannweg 10, D-55128 Mainz, Germany
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/ Reinhard Philipp
  • Fachbereich Chemie/Abteilung Biochemie der Technischen Universität Kaiserslautern, Erwin Schrödinger Str. 54, D-67663 Kaiserslautern, Germany
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/ Raghavan Varadarajan / Dariush Hinderberger
  • Polymer-Spektroskopie, Max-Planck-Institut für Polymerforschung, Ackermannweg 10, D-55128 Mainz, Germany
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  • De Gruyter OnlineGoogle Scholar
/ Wolfgang E. Trommer
  • Fachbereich Chemie/Abteilung Biochemie der Technischen Universität Kaiserslautern, Erwin Schrödinger Str. 54, D-67663 Kaiserslautern, Germany
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Published Online: 2012-07-26 | DOI: https://doi.org/10.1515/BC.2011.151

Abstract

SecB is a homotetrameric cytosolic chaperone that forms part of the protein translocation machinery in E. coli. Due to SecB, nascent polypeptides are maintained in an unfolded translocation-competent state devoid of tertiary structure and thus are guided to the translocon. In vitro SecB rapidly binds to a variety of ligands in a non-native state. We have previously investigated the bound state conformation of the model substrate bovine pancreatic trypsin inhibitor (BPTI) as well as the conformation of SecB itself by using proximity relationships based on site-directed spin labeling and pyrene fluorescence methods. It was shown that SecB undergoes a conformational change during the process of substrate binding. Here, we generated SecB mutants containing but a single cysteine per subunit or an exposed highly reactive new cysteine after removal of the nearby intrinsic cysteines. Quantitative spin labeling was achieved with the methanethiosulfonate spin label (MTS) at positions C97 or E90C, respectively. Highfield (W-band) electron paramagnetic resonance (EPR) measurements revealed that with BPTI present the spin labels are exposed to a more polar/hydrophilic environment. Nanoscale distance measurements with double electron-electron resonance (DEER) were in excellent agreement with distances obtained by molecular modeling. Binding of BPTI also led to a slight change in distances between labels at C97 but not at E90C. While the shorter distance in the tetramer increased, the larger diagonal distance decreased. These findings can be explained by a widening of the tetrameric structure upon substrate binding much like the opening of two pairs of scissors.

Keywords: distance measurements; double electron-electron resonance (DEER); electron paramagnetic resonance (EPR); high-field/high-frequency EPR; SecB mutants; spin labeling

About the article

Corresponding author


Received: 2011-05-06

Accepted: 2011-08-08

Published Online: 2012-07-26

Published in Print: 2011-10-01


Citation Information: Biological Chemistry, Volume 392, Issue 10, Pages 849–858, ISSN (Online) 1437-4315, ISSN (Print) 1431-6730, DOI: https://doi.org/10.1515/BC.2011.151.

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