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Related Concept Videos

Antigen Processing Pathways01:31

Antigen Processing Pathways

MHC molecules are key players in the immune response, enabling T cells to recognize and respond to specific antigens. They are present on the surface of all nucleated cells in the body and are instrumental in presenting antigens to T cells and activating them. T cells recognize the MHC-antigen complex and initiate an immune response. MHC class I and MHC class II are two main types of MHC molecules, each associated with a distinct antigen processing pathway.
MHC Class I: Presenting Endogenous...
Antigens Involved in Adaptive Immunity01:26

Antigens Involved in Adaptive Immunity

An antigen is any substance the immune system identifies as foreign and potentially harmful to the body, prompting an immune response. Antigens have two functional properties: immunogenicity and reactivity. Immunogenicity is the ability of an antigen to stimulate a specific immune response. At the same time, reactivity describes the antigen's ability to react with the cells and antibodies produced in response to it.
Complete Antigens
Complete antigens possess both immunogenicity and reactivity.
Translocation of Proteins into the Mitochondria01:19

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:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
Protein Translocation Machinery on the ER Membrane01:28

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.
Mitochondrial Protein Sorting01:39

Mitochondrial Protein Sorting

Mitochondria are double-membrane organelles of the eukaryotes involved in cellular metabolism, signaling, ATP synthesis, and programmed cell death.  Each of these processes requires specific proteins and enzymes that must be correctly sorted to the right mitochondrial subcompartment for the proper functioning of the organelle.
Most of these mitochondrial proteins are encoded by the nucleus and imported to the mitochondria as unfolded or loosely folded precursors. Mitochondrial precursors...
Protein Transport into the Inner Mitochondrial Membrane01:34

Protein Transport into the Inner Mitochondrial Membrane

Nuclear encoded mitochondrial precursors are imported to the inner membrane in a multistep process involving two separate translocons, TIM22 and TIM23. TIM23 is a cation-selective pore that remains closed by the N terminal segment of the protein. Negative charges on the TIM23 act as a receptor for the incoming precursor, pulling the positively charged matrix-targeting sequence for peptide insertion and translocation.
Transport of mitochondrial precursors across the TIM23 channel is driven by...

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Related Experiment Video

Updated: Jun 23, 2026

Purification of the Membrane Compartment for Endoplasmic Reticulum-associated Degradation of Exogenous Antigens in Cross-presentation
12:48

Purification of the Membrane Compartment for Endoplasmic Reticulum-associated Degradation of Exogenous Antigens in Cross-presentation

Published on: August 21, 2017

The peptide-loading complex--antigen translocation and MHC class I loading.

Christian Schölz1, Robert Tampé

  • 1Institute of Biochemistry, Biocenter, Center for Membrane Proteomics (CMP) and Cluster of Excellence (CEF)-Macromolecular Complexes, Goethe University Frankfurt, Max-von-Laue Str. 9, D-60438 Frankfurt/Main, Germany.

Biological Chemistry
|May 12, 2009
PubMed
Summary
This summary is machine-generated.

The transporter associated with antigen processing moves antigenic peptides into the endoplasmic reticulum for loading onto MHC class I molecules. This process ensures T-lymphocytes recognize infected cells by presenting stable peptide-MHC complexes.

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Last Updated: Jun 23, 2026

Purification of the Membrane Compartment for Endoplasmic Reticulum-associated Degradation of Exogenous Antigens in Cross-presentation
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Stability and Structure of Bat Major Histocompatibility Complex Class I with Heterologous β2-Microglobulin
11:17

Stability and Structure of Bat Major Histocompatibility Complex Class I with Heterologous β2-Microglobulin

Published on: March 10, 2021

Area of Science:

  • Immunology
  • Molecular Biology
  • Cell Biology

Background:

  • Adaptive immunity relies on presenting cellular protein fragments on Major Histocompatibility Complex (MHC) class I molecules.
  • This presentation allows T-lymphocytes to identify infected or cancerous cells.
  • Efficient antigen presentation requires precise translocation into the endoplasmic reticulum (ER).

Purpose of the Study:

  • To review recent findings on antigen translocation into the ER.
  • To focus on the mechanisms of the transporter associated with antigen processing (TAP).
  • To elucidate the loading of peptides onto MHC class I molecules within the ER.

Main Methods:

  • Review of recent scientific literature.
  • Focus on molecular mechanisms of protein translocation.
  • Analysis of peptide-MHC class I complex formation.

Main Results:

  • A dynamic machinery, including the transporter associated with antigen processing, translocates antigenic peptides into the ER lumen.
  • The peptide-loading complex selects high-affinity peptides for stable MHC class I complex formation.
  • This selection is crucial for effective T-lymphocyte recognition.

Conclusions:

  • The transporter associated with antigen processing and the peptide-loading complex are key players in adaptive immunity.
  • Understanding these mechanisms is vital for comprehending immune surveillance.
  • Recent findings highlight the intricate process of antigen presentation.