| Summary: | <p>In this thesis I describe the application of native mass spectrometry to investigate membrane protein interactions with lipids and other small molecules. This work is a combination of method development, resulting in novel ways to study membrane protein-lipid complexes by native mass spectrometry, and application of established techniques to important biological targets.</p>
<p>In chapter 2, I demonstrate for the first time the ability of surface-induced dissociation to distinguish between interfacial and non-interfacial phospholipid binding. Additionally, I show that combining this method with the modern high sensitivity instrumentation and statistical analysis enables the observation of subtle differences in oligomeric stabilities of membrane proteins in the presence of different species of interfacial lipids.</p>
<p>Chapter 3 describes application of native mass spectrometry to the investigation of a selected set of novel and established detergents. Controlled delipidation of membrane proteins is readily achieved by selecting a specific detergent from this set. Furthermore, a protocol for selective removal of either phospholipids or lipopolysaccharide with the aid of these detergents is presented. These findings contribute both towards the practical applications to membrane protein research and also towards a better fundamental understanding of detergents in general.</p>
<p>Chapter 4 describes the use of native mass spectrometry to probe the effects of lipid binding on a horse Na+/H+ transporter, NHE9. I show, that in the absence of specific lipid interactions NHE9 is unable to maintain its dimeric form. These results complement the recently obtained high-resolution structure of this protein.</p>
<p>Finally, chapter 5 illustrates investigation of the human MAPEG protein family. I use collision-induced dissociation experiments to demonstrate the preference of one member of this family, LTC4S, for particular phospholipid classes. I also identify appropriate native mass spectrometry conditions for another member of this family, MGST2, and link its instability to the removal of structurally important lipids by membrane mimetics.</p>
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