The CXXCH motif is usually recognized in the bacterial periplasm as a haem attachment site in apocytochromes c. There is evidence that the Escherichia coli Ccm (cytochrome c maturation) system recognizes little more than the CXXCH sequence. A limited number of periplasmic proteins have this motif and yet are not c-type cytochromes. To explore how unwanted haem attachment to CXXCH might be avoided, and to determine whether haem attachment to the surface of a non-cytochrome protein would be possible, we converted the active-site CXXCK motif of a thioredoxin-like protein into CXXCH, the C-terminal domain of the transmembrane oxidoreductase DsbD (cDsbD). The E. coli Ccm system was found to catalyse haem attachment to a very small percentage of the resultant protein (∼0.2%). We argue that cDsbD folds sufficiently rapidly that only a small fraction fails to avoid the Ccm system, in contrast with bona fide c-type cytochromes that only adopt their tertiary structure following haem attachment. We also demonstrate covalent haem attachment at a low level in vivo to the periplasmic disulfide isomerase DsbC, which contains a native CXXCH motif. These observations provide insight into substrate recognition by the Ccm system and expand our understanding of the requirements for covalent haem attachment to proteins. The possible evolutionary relationship between thioredoxins and c-type cytochromes is discussed.
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December 2008
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Conference Article|
November 19 2008
Avoidance of the cytochrome c biogenesis system by periplasmic CXXCH motifs
Despoina A.I. Mavridou;
Despoina A.I. Mavridou
*Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K.
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Martin Braun;
Martin Braun
†Institut für Mikrobiologie, Eidgenössische Technische Hochschule, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, Switzerland
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Linda Thöny-Meyer;
Linda Thöny-Meyer
1
†Institut für Mikrobiologie, Eidgenössische Technische Hochschule, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, Switzerland
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Julie M. Stevens;
Julie M. Stevens
2
*Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K.
2Correspondence may be addressed to either of these authors (email julie.stevens@bioch.ox.ac.uk or stuart.ferguson@bioch.ox.ac.uk).
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Stuart J. Ferguson
Stuart J. Ferguson
2
*Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K.
2Correspondence may be addressed to either of these authors (email julie.stevens@bioch.ox.ac.uk or stuart.ferguson@bioch.ox.ac.uk).
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Publisher: Portland Press Ltd
Received:
July 29 2008
Online ISSN: 1470-8752
Print ISSN: 0300-5127
© The Authors Journal compilation © 2008 Biochemical Society
2008
Biochem Soc Trans (2008) 36 (6): 1124–1128.
Article history
Received:
July 29 2008
Citation
Despoina A.I. Mavridou, Martin Braun, Linda Thöny-Meyer, Julie M. Stevens, Stuart J. Ferguson; Avoidance of the cytochrome c biogenesis system by periplasmic CXXCH motifs. Biochem Soc Trans 1 December 2008; 36 (6): 1124–1128. doi: https://doi.org/10.1042/BST0361124
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