Electrospray ionization mass spectrometry temperature effects on metal ion: Protein stoichiometries and metal-induced conformational changes in calmodulin

Timothy D. Veenstra, Kenneth L. Johnson, Andy J. Tomlinson, Stephen Naylor, Rajiv Kumar

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

The calcium ion (Ca2+) binding stoichiometry required to induce a complete, tertiary conformational change of calmodulin is still disputed. Several studies have indicated that this occurs upon the uptake of only two Ca2+; more recent reports, however, indicate that four Ca2+ are required. We used electrospray ionization (ESI) mass spectrometry under standard ESI conditions (i.e. high temperature, organic co-solvent) to identify definitively the Ca2+ stoichiometry required to induce a conformational change in the protein, and we demonstrate that four Ca2+ are needed. We then undertook a comparative study on the Ca2+-binding of calmodulin using a lower ESI source temperature. Under these conditions we can detect Ca2+-saturated calmodulin at much lower Ca2+ to protein molar ratios than those observed using typical ESI conditions. This latter observation more closely reflects the solution-phase conditions that are noted using aqueous solution-based spectroscopies to study protein-metal binding.

Original languageEnglish (US)
Pages (from-to)453-459
Number of pages7
JournalEuropean Journal of Mass Spectrometry
Volume3
Issue number6
StatePublished - Dec 1 1997

Keywords

  • Calcium
  • Calmodulin
  • Conformation
  • Electrospray ionization mass spectrometry
  • Low temperature

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Spectroscopy

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