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Role of the twin arginine protein transport pathway in the assembly of the Streptomyces coelicolor cytochrome bc1 complex

Lookup NU author(s): Dr Adam Hopkins, Dr Grant Buchanan, Professor Tracy Palmer FRS FRSE FMedSciORCiD



This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


The cytochrome bc1-cytochrome aa3 complexes together comprise one of the major branches of the bacterial aerobic respiratory chain. In actinobacteria, the cytochrome bc1 complex shows a number of unusual features in comparison to other cytochrome bc1 complexes. In particular, the Rieske iron-sulfur protein component of this complex, QcrA, is a polytopic rather than a monotopic membrane protein. Bacterial Rieske proteins are usually integrated into the membrane in a folded conformation by the twin arginine protein transport (Tat) pathway. In this study, we show that the activity of the Streptomyces coelicolor M145 cytochrome bc1 complex is dependent upon an active Tat pathway. However, the polytopic Rieske protein is still integrated into the membrane in a tatC mutant strain, indicating that a second protein translocation machinery also participates in its assembly. Difference spectroscopy indicated that the cytochrome c component of the complex was correctly assembled in the absence of the Tat machinery. We show that the intact cytochrome bc1 complex can be isolated from S. coelicolor M145 membranes by affinity chromatography. Surprisingly, a stable cytochrome bc1 complex containing the Rieske protein can be isolated from membranes even when the Tat system is inactive. These findings strongly suggest that the additional transmembrane segments of the S. coelicolor Rieske protein mediate hydrophobic interactions with one or both of the cytochrome subunits. © 2014, American Society for Microbiology. All Rights Reserved.

Publication metadata

Author(s): Hopkins A, Buchanan G, Palmer T

Publication type: Article

Publication status: Published

Journal: Journal of Bacteriology

Year: 2014

Volume: 196

Issue: 1

Pages: 50-59

Print publication date: 01/01/2014

Online publication date: 18/10/2013

Acceptance date: 10/10/2013

Date deposited: 15/02/2019

ISSN (print): 0021-9193

ISSN (electronic): 1098-5530

Publisher: American Society for Microbiology


DOI: 10.1128/JB.00776-13

PubMed id: 24142258


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