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Related Concept Videos

Bacterial Translocation and Protein Secretion01:26

Bacterial Translocation and Protein Secretion

Bacterial protein secretion involves translocation systems to ensure proteins reach their designated locations, including the plasma membrane, periplasm, outer membrane, or the external environment. These translocation systems are vital for bacterial physiology, supporting processes like membrane assembly, enzymatic activity in the periplasm, and interactions with the external environment. The division of labor between Sec and Tat pathways ensures efficiency in handling proteins with diverse...
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Protein Translocation Machinery on the ER Membrane

The translocon complex situated on the ER membrane is the main gateway for the protein secretory pathway. It facilitates the transport of nascent peptides into the ER lumen and their insertion into the ER membrane.
Sec61 protein conducting channel
In eukaryotes, the translocon complex comprises a core heterotrimeric translocator channel called the Sec61 complex. This channel includes three transmembrane proteins, Sec61α, Sec61β, and Sec61γ, and is the largest subunit of the translocon complex.
Structure of Porins01:21

Structure of Porins

Mitochondria, chloroplasts, and gram-negative bacteria have transmembrane, beta-barrel proteins called porins to mediate the free diffusion of ions and metabolites across the membrane. Mitochondrial porin precursors contain conserved amino acid sequences called beta signals at their C-terminal. Beta signals have a  motif of PoXGXXHyXHy (Po-Polar, X-Any amino acid, G-Glycine, Hy-LargeHydrophobic), which are crucial for precursor recognition to initiate precursor assembly. Beta-barrel precursors...
Porin Insertion in the Outer Mitochondrial Membrane01:12

Porin Insertion in the Outer Mitochondrial Membrane

Porins are beta-barrel proteins translocated to the mitochondrial outer membrane through the TOM complex into the intermembrane space. Porin precursors bind TIM chaperones within the intermembrane space and are guided to the Sorting and Assembly Machinery complex or SAM complex on the outer mitochondrial membrane.
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Translocation of Proteins into the Mitochondria

Mitochondrial precursors are translocated to the internal subcompartments via independent mechanisms involving distinct protein machineries called translocases.
Sorting of outer membrane proteins:
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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):...

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Directed Protein Packaging within Outer Membrane Vesicles from Escherichia coli: Design, Production and Purification
10:21

Directed Protein Packaging within Outer Membrane Vesicles from Escherichia coli: Design, Production and Purification

Published on: November 16, 2016

Periplasmic export machines for outer membrane assembly.

Chris Whitfield1, James H Naismith

  • 1Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada. cwhitfie@uoguelph.ca

Current Opinion in Structural Biology
|May 23, 2008
PubMed
Summary
This summary is machine-generated.

Gram-negative bacteria outer membrane assembly is complex. New research reveals a molecular scaffold for exporting group 1 capsular polysaccharides, advancing our understanding of this vital bacterial structure.

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Area of Science:

  • Microbiology
  • Molecular Biology
  • Structural Biology

Background:

  • The Gram-negative bacterial cell envelope provides crucial protection but presents assembly challenges, especially for the outer membrane.
  • While outer membrane protein assembly is well-studied, export and assembly of complex glycoconjugates remain less understood.

Purpose of the Study:

  • To elucidate the mechanisms of complex glycoconjugate export and assembly in the Gram-negative bacterial outer membrane.
  • To identify key molecular components involved in the transport of group 1 capsular polysaccharides.

Main Methods:

  • Utilized structural biology techniques to determine the architecture of the export machinery.
  • Employed biochemical assays to investigate the function of identified molecular components.

Main Results:

  • Identified a novel envelope-spanning molecular scaffold essential for group 1 capsular polysaccharide export.
  • Provided new structural and biochemical insights into a complex molecular machine responsible for outer membrane glycoconjugate assembly.

Conclusions:

  • The discovered molecular scaffold is critical for efficient glycoconjugate transport across the bacterial envelope.
  • This work advances the understanding of outer membrane biogenesis and offers potential targets for antimicrobial strategies.