The C-terminal domain of the Pseudomonas secretin XcpQ forms oligomeric rings with pore activity
| Autor: | Patrick Van Gelder, Ronald G. P. M. Brok, Margot Koster, Hans de Cock, Ulrike Ziese, Jan Tommassen, Abraham J. Koster, Wilbert Bitter, Mathias Winterhalter |
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| Rok vydání: | 1999 |
| Předmět: |
Lipid Bilayers
Porins Secretin family Protein Structure Secondary Structure-Activity Relationship Bacterial Proteins Structural Biology Pseudomonas Trypsin Secretion Protein Structure Quaternary Molecular Biology Conserved Sequence Sequence Homology Amino Acid biology Circular Dichroism C-terminus Electric Conductivity Membrane Proteins Translocon biology.organism_classification Recombinant Proteins Pseudomonas alcaligenes Protein Structure Tertiary Molecular Weight Microscopy Electron Biochemistry Genes Bacterial Mutation Pseudomonas aeruginosa Endopeptidase K Alcaligenes Crystallization Bacterial outer membrane |
| Zdroj: | ResearcherID |
| ISSN: | 0022-2836 |
| DOI: | 10.1006/jmbi.1999.3340 |
| Popis: | The Pseudomonas secretin XcpQ forms an oligomeric complex, which is involved in the translocation of proteins across the outer membrane via the type II secretion pathway. Pseudomonas aeruginosa produces only small amounts of this complex, 50 to 100 copies per bacterium, and overexpression is lethal to these cells. However, overexpression of Pseudomonas alcaligenes XcpQ could be achieved in the P. alcaligenes mutant strain 537. Protease protection experiments with P. alcaligenes XcpQ showed that the C-terminal domain of XcpQ, which is conserved in all the different members of the secretin family, is largely resistant to proteinase K. This protease-resistant fragment is embedded in the membrane and remains a stable complex, indicating that this domain is involved in complex formation. Both the intact and the protease-protected XcpQ complex showed a tendency to form two-dimensional crystal-like structures. Electron microscopic analysis of these structures showed that the overall oligomeric rings of the intact and of the protease-resistant complex are highly similar. The central cavity of the intact XcpQ complex contains structured mass. Both the intact and the protease-protected XcpQ complex showed pore-forming activity in planar lipid bilayers, consistent with their role as a translocation channel. However, the single-channel conductances observed were not uniform. Together, these results demonstrate that the C-terminal secretin homology domain of XcpQ is the structural domain that forms the channel through which macromolecules are being transported. |
| Databáze: | OpenAIRE |
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