Disordered Motifs and Domains in Cell Control
Sunday Speaker Abstracts
The Use of Mass Spectrometry to Determine the Disordered Content of Proteins
Rebecca Beveridge
1
, Kamila Parcholarz
2
, Jason Kalapothakis
2
, Cait MacPhee
2
,
Perdita
Barran
1
.
1
The University of Manchester, Manchester, United Kingdom,
2
The University of Edinburgh,
Edinburgh, United Kingdom.
In the last decade mass spectrometry (MS) coupled with electrospray ionisation (ESI) has been
extensively applied to the study of intact proteins and their complexes. Solvent conditions, for
example pH, buffer strength and concentration, affect the observed desolvated species; the ease
of altering such extrinsic factors render ESI-MS an appropriate method by which to consider the
range of conformational states that proteins may occupy including natively folded, disordered
and amyloid. Rotationally averaged collision cross sections of the ionised forms of proteins,
provided by the combination of mass spectrometry and ion mobility (IM-MS), are also
instructive in exploring conformational landscapes in the absence of solvent. We have selected
19 different proteins, both monomeric and multimeric, ranging in mass from 2846 Da (melittin)
to 150 kDa (Immunoglobulin G) and we consider how they present to the mass spectrometer
under different solvent conditions. Mass spectrometery distinguishes which of these proteins are
structured from those that contain regions of disorder by considering two experimental
parameters; Dz (the range of charge states occupied by the protein) and DCCS (the range of
collision cross sections that the protein is observed in). We provide a simple model which allows
the theoretical prediction of the smallest and largest possible collision cross sections based on the
volume of the amino acids in the sequences, and we compare these calculated parameters with
the experimental values. the intensities of ions in the mass spectra is used to provide occupancy
of conformational states allowing us to qualitatively predict the potential energy landscape of
each protein. This empirical approach to assess order or disorder has more accuracy than
theoretical methods based on the amino acid sequences for the chosen systems, and could
provide an initial route to characterisation.
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