Native mass spectrometry (MS) of proteins and protein assemblies reveals size and stoichiometry. But elucidating their structures to understand their function is more challenging. What “structures” are really being probed by native MS? As defined by Leney and Heck in 2017, the term “native” in “native MS” refers only to the biological status of the protein/biological assembly in solution prior to mass analysis. But to what extent are native protein structures preserved in the gas-phase (and are being measured by MS)? Using electrospray ionization (ESI), relative charging by native ESI-MS appears to give some information on protein folding. We show that native MS and native top-down MS can be effective for deriving structural information for soluble and membrane protein complexes, and much of this information can be correlated to the solution-phase structure.Native top-down MS generates information on the surface topology, ligand binding sites, and post-translational modifications (PTMs) of protein complexes. We use native MS/MS to investigate the molecular action of compounds that prevent amyloid fibril formation in neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease.The importance of salt bridges, those that are suggested to be present in the solution-phase structure and perhaps newly formed in the gas-phase structure, in the dissociation behavior of gas-phase proteins will be discussed. Ion mobility MS suggests the alteration of a protein’s gas-phase structure by some PTMs. But as posed over 20-years ago in a review published in 1997, “Is there any utility in studying the structure of the gas-phase protein complex?”, this question is still of importance to the field.

Native mass spectrometry: Probing gas-phase or solution-phase protein structures?

2019 Fall National Meeting

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