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Assembly of the MHC I peptide-loading complex determined by a conserved ionic lock-switch

Andreas Blees1, Katrin Reichel2,3, Simon Trowitzsch1

  • 1Institute of Biochemistry, Biocenter, Goethe-University Frankfurt am Main, Max-von-Laue-Str. 9, D-60438 Frankfurt am Main, Germany.

Scientific Reports
|November 28, 2015
PubMed

Insights

A newly identified salt bridge between TAP and tapasin is crucial for the peptide-loading complex (PLC) assembly and MHC I antigen presentation, revealing a key immune system interaction.

Area of Science:

  • Immunology
  • Structural Biology
  • Molecular Biophysics

Background:

  • Salt bridges in lipid bilayers are vital for immune receptor assembly and signaling.
  • The peptide-loading complex (PLC) presents self-antigens and peptides via MHC class I molecules.
  • Understanding PLC dynamics is key to immune system function.

Purpose of the Study:

  • To identify and characterize salt bridges within the peptide-loading complex (PLC).
  • To investigate the role of a specific salt bridge in PLC assembly and function.
  • To elucidate the mechanism of interaction between TAP and tapasin.

Main Methods:

  • Identification of inter-subunit salt bridges in membrane protein complexes.
  • Molecular modeling and simulation techniques.
  • All-atom molecular dynamics simulations.

Main Results:

  • A single salt bridge between the transporter associated with antigen processing (TAP) and tapasin was identified.
  • This salt bridge is essential for the assembly of the PLC.
  • The salt bridge is critical for efficient MHC class I antigen presentation.
  • An ionic lock-switch mechanism explains TAP-tapasin binding, preventing charge imbalance in the ER membrane.

Conclusions:

  • The TAP-tapasin salt bridge is a critical determinant for PLC assembly and function.
  • This interaction highlights a general principle for dynamic multiprotein membrane complex assembly in immunity.
  • Findings deepen the understanding of immune complex interactions and antigen presentation.

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