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Updated: Jan 25, 2026

Combining Chemical Cross-linking and Mass Spectrometry of Intact Protein Complexes to Study the Architecture of Multi-subunit Protein Assemblies
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Combining Chemical Cross-linking and Mass Spectrometry of Intact Protein Complexes to Study the Architecture of Multi-subunit Protein Assemblies

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Subunit pI Can Influence Protein Complex Dissociation Characteristics.

Aneika C Leney1

  • 1School of Biosciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK. a.leney@bham.ac.uk.

Journal of the American Society for Mass Spectrometry
|May 12, 2019
PubMed
Summary
This summary is machine-generated.

Isoelectric points (pI) of protein subunits significantly impact gas-phase dissociation in mass spectrometry. Understanding subunit pI is crucial for accurately determining protein complex topology using tandem mass spectrometry.

Keywords:
Collision-induced dissociationIsoelectric pointNative mass spectrometryPhycobiliproteinsProtein complex dissociation

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Area of Science:

  • Biochemistry
  • Analytical Chemistry
  • Structural Biology

Background:

  • Mass spectrometry is a key technique for analyzing protein complex topology.
  • Gas-phase dissociation mechanisms are increasingly understood but dissociation outcomes can be unpredictable.
  • Protein complex composition analysis relies on inferring information from dissociation patterns.

Purpose of the Study:

  • To investigate the influence of individual protein subunit isoelectric points (pI) on gas-phase complex dissociation.
  • To determine if subunit pI affects the predictability of protein complex dissociation in mass spectrometry.
  • To elucidate the role of pI in interpreting tandem mass spectrometry data for protein complex topology.

Main Methods:

  • Comparison of gas-phase dissociation patterns for two structurally similar hexameric protein complexes: allophycocyanin and phycoerythrin.
  • Analysis of protein complexes with alternating alpha and beta subunits, differing in subunit pI (allophycocyanin) or having identical pI (phycoerythrin).
  • Utilizing tandem mass spectrometry to observe dissociation products.

Main Results:

  • Phycoerythrin dissociation yielded both alpha and beta monomeric subunits, as predicted.
  • Allophycocyanin dissociation resulted in the detection of only the alpha monomeric subunit, a deviation from prediction.
  • Distinct pIs of allophycocyanin subunits influenced dissociation outcomes, while identical pIs in phycoerythrin did not.

Conclusions:

  • The isoelectric point (pI) of individual protein subunits is a critical factor influencing gas-phase dissociation behavior.
  • Tandem mass spectrometry data interpretation for protein complex topology must account for subunit pI differences.
  • Subunit pI heterogeneity can lead to differential dissociation, impacting the inferred composition of protein complexes.