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Conjugative Mating Assays for Sequence-specific Analysis of Transfer Proteins Involved in Bacterial Conjugation
Published on: January 4, 2017
Structure of the outer membrane complex of a type IV secretion system
Vidya Chandran1, Rémi Fronzes, Stéphane Duquerroy
1Institute of Structural and Molecular Biology, University College London and Birkbeck College, Malet Street, London WC1E 7HX, UK.
Nature
|December 1, 2009
Summary
Type IV secretion systems are bacterial nanomachines. This study reveals the outer membrane channel structure, identifying VirB10 as the key protein spanning both bacterial membranes.
Area of Science:
- Microbiology
- Structural Biology
- Biochemistry
Background:
- Type IV secretion systems (T4SS) are essential nanomachines in Gram-negative bacteria, spanning both inner and outer membranes.
- The T4SS core complex, comprising VirB7, VirB9, and VirB10 proteins, is crucial for substrate translocation.
- Understanding the structure of the outer membrane component is vital for deciphering secretion mechanisms.
Purpose of the Study:
- To determine the high-resolution structure of the T4SS outer membrane complex.
- To elucidate the role of individual proteins, particularly VirB10, in forming the outer membrane channel.
- To investigate the structural basis for channel regulation.
Main Methods:
- X-ray crystallography was employed to determine the structure of the outer membrane complex (approximately 0.6 MDa).
- Cryo-electron microscopy (cryo-EM) data was used for comparative structural analysis.
- Biochemical and biophysical techniques were utilized to characterize the complex.
Main Results:
- The crystal structure of the complete outer membrane complex, composed of VirB7, VirB9, and VirB10, was determined.
- VirB10 was identified as the central component of the outer membrane channel, featuring a unique hydrophobic double-helical transmembrane region.
- This work establishes VirB10 as the sole protein known to traverse both bacterial membranes within the T4SS.
- Structural comparisons revealed potential conformational changes linked to channel gating.
Conclusions:
- The solved structure provides unprecedented insight into the architecture of the T4SS outer membrane channel.
- VirB10 plays a critical role in forming the transmembrane pore and is essential for T4SS function.
- Conformational plasticity of the channel suggests a mechanism for regulating substrate passage.
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