| Summary: | <p>Interactions between membrane proteins and their surrounding lipids play an integral
role in coordinating membrane function. However, capturing and differentiating key
lipid binding to membrane proteins within the complex and the dynamic membrane
environment remains challenging for existing methods. Recent developments in
native mass spectrometry have enabled non-covalent interactions of protein
complexes to be maintained in the gas phase allowing critical membrane protein-lipid
interactions in biological systems to be probed. In this thesis, native mass
spectrometry is used throughout, sometimes coupled with liquid
chromatography-mass spectrometry based lipidomics, to interrogate membrane
proteins and their natural lipid environments.</p>
<p>A protocol to control the degree of delipidation from membrane proteins was
developed (Chapter 2). The resulting mass spectra revealed the target membrane
proteins, MsbA and MdtK, in different lipid bound states, enabling the relationship
between membrane proteins and neighbouring lipids to be observed. Next MS was
used to characterise a novel detergent-free particle known as a lipodisq (Chapter 3).
Lipodisqs encapsulate membrane proteins in their original lipid environment. By
optimising lipodisq preparation and MS methodology, well-resolved MS spectra of
rhodopsin and MdtK with bound lipids from their lipodisq preparations were obtained.
Finally, MS was used in conjunction with cryo-EM to investigate a respiratory protein
supercomplex (Chapter 4). MS not only provided mass information which assisted in
the identification of the protein subunits and binding lipids, but also detected the
non-covalent interactions between protein and other ligand molecules in the
supercomplex system. Overall, the research reported in this thesis has contributed to
broadening the applications of mass spectrometry in the emerging field of protein-lipid
interactions. </p>
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