Structural characterization of different proteins as potential drug targets

Structure determination of proteins is key to understanding their function and mechanism of action. In this thesis the structural characterization of three proteins by X-ray crystallography is described. The human Aryl hydrocarbon Receptor (AhR) is an important transcription factor which has been known for a long time to be involved in several regulatory processes and immune-system adaptation. Its first structural characterizations only emerged in very recent years as its stability in solution is precarious. Despite our numerous attempts to produce a soluble construct, it was not possible to conduct any structural characterization of AhR given its very low stability in solution. The Main Protease (Mpro) of SARS-CoV-2 is an essential enzyme for the virus maturation and replication. We extensively characterized this protein both in its wild-type variant and in several mutants developed in our laboratory with the aim to bet-ter understand its enzymatic mechanism and binding dynamics. A novel conformation of the wild-type variant of Mpro and several structures of mutants in pres-ence of inhibitors and endogenous substrates are hereby described. The first experimental structure of murine Threonine Aldolase (Tha-1) enzyme was determined in presence and in absence of its PLP cofactor. These structures were important for the validation of a reverse-docking algorithm and provide the first structural evidence of a mammalian Threonine Aldolase enzyme.