Related Experiment Video

Updated: May 31, 2026

Epithelial Cell Infection Analyses with Shigella
04:56

Epithelial Cell Infection Analyses with Shigella

Published on: February 9, 2024

Structural and functional studies on the N-terminal domain of the Shigella type III secretion protein MxiG

Melanie A McDowell1, Steven Johnson1, Janet E Deane1

  • 1Sir William Dunn School of Pathology, University of Oxford, Oxford OX1 3RE, United Kingdom.

The Journal of Biological Chemistry
|July 8, 2011
PubMed

Insights

The MxiG N-terminal domain (MxiG-N) of Shigella flexneri

Area of Science:

  • Microbiology
  • Structural Biology
  • Molecular Biology

Background:

  • MxiG is a key component of the Shigella flexneri type III secretion system (T3SS).
  • The cytoplasmic MxiG N-terminal domain (MxiG-N) function in T3SS assembly is poorly understood.
  • The T3SS is crucial for bacterial pathogenesis.

Purpose of the Study:

  • Determine the structure of MxiG-N(6-112).
  • Investigate the function of MxiG-N in T3SS assembly and secretion.
  • Clarify the role of MxiG-N in the T3SS stoichiometry.

Main Methods:

  • Solution structure determination of MxiG-N(6-112) using NMR spectroscopy.
  • Site-directed mutagenesis of putative phosphate-binding residues.
  • Analysis of T3SS assembly and function in Shigella flexneri.

Main Results:

  • The first solution structure of MxiG-N(6-112) was determined, revealing homology to forkhead-associated (FHA) domains.
  • MxiG-N(6-112) lacks canonical phosphothreonine binding capabilities.
  • Mutagenesis studies showed no impact on T3SS assembly or function, indicating a novel role for MxiG-N.
  • Structural modeling supports a stoichiometry of 24 MxiG subunits in the T3SS inner membrane ring.

Conclusions:

  • MxiG-N possesses a novel function distinct from canonical FHA domains.
  • The MxiG-N structure provides insights into the T3SS inner membrane ring organization.
  • This study advances understanding of T3SS structure and function in Shigella flexneri.

More Related Videos

Production of Disulfide-stabilized Transmembrane Peptide Complexes for Structural Studies12:05

Production of Disulfide-stabilized Transmembrane Peptide Complexes for Structural Studies

Published on: March 6, 2013

Imaging Ca2+ Responses During Shigella Infection of Epithelial Cells08:56

Imaging Ca2+ Responses During Shigella Infection of Epithelial Cells

Published on: May 24, 2018

Related Concept Videos

Overview of Secretory Vesicles01:33

Overview of Secretory Vesicles

Secretory vesicles, also known as dense core vesicles (DCVs), are membrane-bound vesicles that transport secretory proteins, such as hormones or neurotransmitters. Regulated secretory vesicles transport proteins from the trans-Golgi network to the exterior of the cell. Proteins present in regulated secretory vesicles are required to be rapidly exocytosed in large amounts upon a specific stimulus.
Various proteins regulate the aggregation of molecules inside the secretory vesicles. Chromogranins...
Tail-anchoring of Proteins in the ER Membrane01:45

Tail-anchoring of Proteins in the ER Membrane

Tail-anchored, or TA, proteins are estimated to make up to 3-5% of membrane proteins found in the eukaryotic cell. Such proteins have a single transmembrane domain located approximately 30 amino acid residues upstream from the C-terminal end. As a result, the signal recognition particle (SRP) cannot guide a TA protein to the ER membrane for cotranslational insertion. Hence, they are integrated into the ER membrane post-translationally using their C-terminal end as the anchor. TA proteins...
Gram-negative Bacterial Protein Secretion Systems01:17

Gram-negative Bacterial Protein Secretion Systems

Gram-negative bacteria utilize sophisticated protein secretion systems to transport proteins across their double-membrane envelope into the extracellular environment or host cells. Based on their mechanism of action, these systems are classified into one-step and two-step pathways.One-Step Secretion Systems (Types I, III, IV, and VI)One-step secretion systems bypass the periplasm entirely, forming a continuous channel that spans both the inner and outer membranes:Type I Secretion System (T1SS):...
Insertion of Single-pass Transmembrane Proteins in the RER01:26

Insertion of Single-pass Transmembrane Proteins in the RER

Integral membrane proteins are proteins adhered to the lipid bilayer of a cell organelle or membrane. They can be of two types: transmembrane integral proteins that span the lipid bilayer and monotopic proteins that are attached to either side of the membrane but do not pass through it.
Integral transmembrane proteins possess transmembrane and extra membrane domains. The transmembrane domains are primarily made of 20-25 hydrophobic amino acids arranged in a helical secondary confirmation. These...
Pinching-off of Coated Vesicles01:32

Pinching-off of Coated Vesicles

Vesicle budding is orchestrated by distinct cytosolic proteins such as adaptor proteins, coat proteins, and GTPases. To initiate vesicle budding, membrane-bending proteins containing crescent-shaped BAR domains bind to the lipid heads in the bilayer and distort the membrane to form a protein-coated vesicle bud. Adaptors proteins such as AP2 for clathrin-coated vesicles can nucleate on the deformed membrane. Finally, coat proteins such as clathrin or COPI and COPII assemble into a coat forming...