Minor pseudopilin self-assembly primes type II secretion pseudopilus elongation
David A Cisneros1, Peter J Bond, Anthony P Pugsley
1Unité de Génétique moléculaire, Départements de Microbiologie et Biologie Structurale et Chimie, Institut Pasteur, Paris, France. cisneros@pasteur.fr
The EMBO Journal
|December 14, 2011
Summary
Minor pseudopilins PulI, PulJ, and PulK initiate type II secretion systems (T2SS) assembly in Gram-negative bacteria. Their self-assembly primes pseudopilus formation, enabling efficient protein secretion.
Area of Science:
- Microbiology
- Molecular Biology
- Structural Biology
Background:
- Type II secretion systems (T2SS) in Gram-negative bacteria utilize pseudopilus filaments for protein secretion.
- The molecular functions of minor pseudopilins PulI, PulJ, and PulK in T2SS assembly remain largely unknown.
Purpose of the Study:
- To elucidate the molecular mechanism of PulI, PulJ, and PulK in initiating pseudopilus assembly.
- To understand how these minor pseudopilins contribute to protein secretion via T2SS.
Main Methods:
- Molecular dynamics simulations
- Bacterial two-hybrid assays
- Cysteine crosslinking
- Functional analysis of protein secretion
Main Results:
- PulI and PulJ form a staggered complex in the plasma membrane, nucleating filament assembly.
- PulK binding to the PulI-PulJ complex causes partial membrane extraction and a register shift, facilitating pseudopilus assembly.
- These minor pseudopilins prime assembly without controlling filament length or secretin channel opening.
Conclusions:
- PulI, PulJ, and PulK self-assembly is crucial for initiating T2SS pseudopilus assembly.
- The observed mechanism suggests a thermodynamically coupled process that initiates the secretion machinery.
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