The relationship between the structure, charge state, and original solution of protein ions remains challenging to decouple. Understanding this relationship is important for interpreting results from ion mobility mass spectrometry experiments, particularly in the context of structural biology. To investigate this relationship, my lab uses ion mobility to probe the structures of the products of cation-to-anion proton-transfer reactions (CAPTR), which uses proton transfer from <i>m</i>/<i>z</i>-selected protein cations to monoanions to generate a long series of charge-reduced products. Using this strategy to investigate protein ions from denatured conditions, we found that the collision cross sections (Ω) of the CAPTR products depend strongly on their charge state. Here, I will discuss the use of this strategy to investigate the effects of charge state on the structures of native-like ions of multiprotein complexes and ions of N-to-C terminal linked polyubiquitins, which were generated from both denaturing and native-like conditions. For the native-like ions, the Ω of the CAPTR products were similar to those of the precursor ions. This result suggests that the excess charges on the precursor ions do not significantly affect their structures. For the polyubiquitin ions from denaturing conditions, the Ω of the CAPTR products decrease with decreasing charge state, but are always at least as large as the Ω of the corresponding native-like ions. This result suggests that the CAPTR products fold to structures that prevent their collapse to more compact random globules.

Effects of charge state on the structures of protein ions: Results from cation-to-anion proton-transfer reactions (CAPTR)

254th National Meeting (2017)

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