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Related Concept Videos

Energy to Drive Translocation01:37

Energy to Drive Translocation

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Mitochondrial protein import is powered by two distinct energy sources: ATP hydrolysis and electrochemical potential across the inner membrane. Newly synthesized precursors are bound by cytosolic chaperones of the Hsp70 family, which guide them to the import receptors on the mitochondrial surface. Utilizing the energy of ATP hydrolysis, Hsp70 chaperones transfer these precursors to the TOM receptors on the mitochondrial outer membrane.
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Translocation of proteins across membranes is an ancient process that occurs even in bacteria and archaebacteria. In fact, the components of the translocation machinery are still conserved between prokaryotes and eukaryotes.
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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.
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Bacterial conjugation is a mechanism of horizontal gene transfer that enables the exchange of genetic material between bacterial cells through direct contact. This process is facilitated by a donor cell carrying a conjugative plasmid, which encodes genes necessary for pilus formation, DNA replication, and transfer. The conjugative plasmid plays a central role in initiating and executing the transfer of genetic material.The tra region of the conjugative plasmid encodes proteins responsible for...
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Translocation of Proteins into the Mitochondria01:19

Translocation of Proteins into the Mitochondria

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Mitochondrial precursors are translocated to the internal subcompartments via independent mechanisms involving distinct protein machineries called translocases.
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Bacterial Translocation and Protein Secretion

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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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Related Experiment Video

Updated: Dec 22, 2025

Detection of Toxin Translocation into the Host Cytosol by Surface Plasmon Resonance
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Detection of Toxin Translocation into the Host Cytosol by Surface Plasmon Resonance

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Tetanus Toxin cis-Loop Contributes to Light-Chain Translocation.

Madison Zuverink1, Matthew Bluma1, Joseph T Barbieri2

  • 1Microbiology and Immunology, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.

Msphere
|May 8, 2020
PubMed
Summary

Researchers identified a specific loop in tetanus toxin (TT) crucial for translocating its light chain (LC) into cells. This discovery sheds light on how clostridial neurotoxins deliver their toxic payload, independent of pore formation.

Keywords:
Clostridiumcell biologyexotoxinsprotein translocationtetanustoxins

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A High-throughput-compatible FRET-based Platform for Identification and Characterization of Botulinum Neurotoxin Light Chain Modulators
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Transmembrane Domain Oligomerization Propensity determined by ToxR Assay
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Transmembrane Domain Oligomerization Propensity determined by ToxR Assay

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Related Experiment Videos

Last Updated: Dec 22, 2025

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A High-throughput-compatible FRET-based Platform for Identification and Characterization of Botulinum Neurotoxin Light Chain Modulators
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Transmembrane Domain Oligomerization Propensity determined by ToxR Assay
06:45

Transmembrane Domain Oligomerization Propensity determined by ToxR Assay

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Area of Science:

  • Molecular Biology
  • Toxinology
  • Cellular Biochemistry

Background:

  • Clostridial neurotoxins (CNTs), including tetanus toxin (TT) and botulinum neurotoxin (BoNT), are produced as single proteins cleaved into light (LC) and heavy chains (HC).
  • The LC is a zinc metalloprotease targeting SNARE proteins, while the HC facilitates cell entry via translocation and binding domains.
  • HCN-mediated LC translocation across the cell membrane is a poorly understood mechanism in CNT action.

Purpose of the Study:

  • To investigate the mechanism of TT-mediated LC translocation using a β-lactamase (βlac) reporter system.
  • To identify specific domains or residues within the HCN responsible for LC translocation.
  • To determine if LC translocation is linked to HCN-mediated pore formation.

Main Methods:

  • Utilized a discovery-based live-cell assay employing a β-lactamase reporter genetically fused to tetanus toxin (βlac-TT).
  • Performed directed mutagenesis to probe the function of specific amino acid residues and loops within the HCN.
  • Conducted molecular simulations to analyze the interaction of the HCN with cell membranes.

Main Results:

  • A charged loop (767DKE769), termed the 'cis-loop,' connecting α15 and α16 within the HCN, was identified as critical for LC translocation.
  • Mutagenesis of this cis-loop, particularly substitution of K768, inhibited LC translocation but not cell binding, intracellular trafficking, or pore formation.
  • Molecular simulations indicated the cis-loop does not directly bind to the cell membrane during translocation.

Conclusions:

  • The cis-loop, specifically K768, plays a vital role in HCN-mediated LC translocation, acting independently of pore formation.
  • This conserved motif across CNTs suggests a common mechanism for catalytic domain delivery.
  • The findings provide new insights into the least understood step of CNT action: protein translocation across the cell membrane.