Sizing large proteins and protein complexes by electrospray ionization mass spectrometry and ion mobility

  • Catherine S. Kaddis
  • Shirley H. Lomeli
  • Sheng Yin
  • Beniam Berhane
  • Marcin I. Apostol
  • Valerie A. Kickhoefer
  • Leonard H. Rome
  • Joseph A. Loo
Focus: From Mobilities To Proteomes

Abstract

Mass spectrometry (MS) and ion mobility with electrospray ionization (ESI) have the capability to measure and detect large noncovalent protein-ligand and protein-protein complexes. Using an ion mobility method of gas-phase electrophoretic mobility molecular analysis (GEMMA), protein particles representing a range of sizes can be separated by their electrophoretic mobility in air. Highly charged particles produced from a protein complex solution using electrospray can be manipulated to produce singly charged ions, which can be separated and quantified by their electrophoretic mobility. Results from ESI-GEMMA analysis from our laboratory and others were compared with other experimental and theoretically determined parameters, such as molecular mass and cryoelectron microscopy and X-ray crystal structure dimensions. There is a strong correlation between the electrophoretic mobility diameter determined from GEMMA analysis and the molecular mass for protein complexes up to 12 MDa, including the 93 kDa enolase dimer, the 480 kDa ferritin 24-mer complex, the 4.6 MDa cowpea chlorotic mottle virus (CCMV), and the 9 MDa MVP-vault assembly. ESI-GEMMA is used to differentiate a number of similarly sized vault complexes that are composed of different N-terminal protein tags on the MVP subunit. The average effective density of the proteins and protein complexes studied was 0.6 g/cm3. Moreover, there is evidence that proteins and protein complexes collapse or become more compact in the gas phase in the absence of water.

Supplementary material

13361_2011_180701206_MOESM1_ESM.doc (176 kb)
Supplementary material, approximately 180 KB.

Copyright information

© American Society for Mass Spectrometry 2007

Authors and Affiliations

  • Catherine S. Kaddis
    • 1
  • Shirley H. Lomeli
    • 1
  • Sheng Yin
    • 1
  • Beniam Berhane
    • 1
  • Marcin I. Apostol
    • 1
  • Valerie A. Kickhoefer
    • 2
  • Leonard H. Rome
    • 2
  • Joseph A. Loo
    • 1
    • 2
  1. 1.Department of Chemistry and Biochemistry, David Geffen School of MedicineUniversity of California-Los AngelesLos AngelesUSA
  2. 2.Department of Biological Chemistry, David Geffen School of MedicineUniversity of California Los AngelesLos AngelesUSA

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