In recent years, fragment-based drug discovery (FBDD) has become established as one of the mainstream methods applied in small molecule drug discovery. In this approach, libraries of small molecular weight compounds known as fragments are screened against a target protein, followed by the development of screening hits into lead candidates through various approaches such as linking, merging, or growing of fragment hits. Emphasis in the field is the ongoing development of highly sensitive analytical methods, like nuclear magnetic resonance, surface plasmon resonance and native state mass spectrometry to detect the weak binding interactions of the fragments with the target protein. But the success of FBDD relies not only on the method used for screening fragments, a target protein sample of excellent quality is equally important. The expression and purification of the candidate target protein can be challenging, especially for important therapeutic targets such as membrane proteins, and requires a significant amount of work that is often underestimated. This thesis is focused on this important issue.

In preparation for future FBDD studies, this work focuses on the characterisation of two membrane proteins, the human glutamine transporter ASCT2 and the G protein-coupled receptor GPR55 and a purportedly soluble protein, carbonic anhydrase from Plasmodium falciparum that have relevance in disease biology but so far have not been subjected to significant screening campaigns. […]