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Charge Reduction of Membrane Proteins in Native Mass Spectrometry Using Alkali Metal Acetate Salts

preprint
submitted on 05.12.2019 and posted on 13.12.2019 by John T. Petroff II, Ailing Tong, Lawrence Chen, GregoryT. DeKoster, Farha Khan, Jeff Abramson, Carl Frieden, Wayland Cheng

Native mass spectrometry paired with ion mobility (IM-MS) provides the capacity to monitor the structure of protein complexes and simultaneously assess small molecule binding to the protein. Native IM-MS typically utilizes positive mode electrospray ionization producing a distribution of multiply charged protein species. For membrane proteins, these charge states are often too high resulting in protein gas phase unfolding or loss of noncovalent interactions. In an effort to reduce the charge of membrane proteins, the utility of alkali metal salts as a charge reducing additive was explored. Low concentrations of alkali metal salts caused marked charge reduction in the membrane protein, ELIC. The charge reducing effect was only present in membrane proteins, and could not be accounted for by conformational changes in ELIC structure. Charge reduction by alkali metal salts was also detergent dependent, and was most pronounced in long PEG-based detergents such as C10E5 and C12E8. Based on these results, a mechanism was posited for alkali metal charge reduction of membrane proteins. Addition of low concentration of alkali metals may provide an advantageous approach for charge reduction of detergent solubilized membrane proteins by native MS.

Funding

Characterizing Neurosteroid Binding in the GABA(A) Receptor Using Top-Down Mass Spectrometry

National Institute of General Medical Sciences

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CIMED Pilot Grant, Washington University

History

Email Address of Submitting Author

wayland.cheng@wustl.edu

Institution

Washington University in St. Louis

Country

USA

ORCID For Submitting Author

0000-0002-9529-9820

Declaration of Conflict of Interest

No conflict of interest

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