Structural Control of Metallothionein Metallation and Oxidation
Abstract
Metallothioneins (MT) are a family of cysteine-rich metal-binding intrinsically disordered proteins that are ubiquitous across life. The proposed functions of MTs are to maintain Zn(II) homeostasis, participate in heavy metal detoxification, and protect against oxidative stress by binding to a variety of metals in a range of stoichiometries. However, due to their disordered nature and ability to form multiple metallated species, these diverse structures are not well characterized. Electrospray ionization mass spectrometry (ESI-MS) is a technique that allows quantification of heterogeneous metallation states through analysis of the speciation distributions. In this thesis, ESI-MS in combination with other spectroscopic techniques is used to probe the structural features of apo-MT, the early Zn(II) and Cd(II) metallation steps, the binding of the xenobiotic metal Bi(III), and the pathway of oxidation and subsequent Zn(II) and Cd(II) displacement upon exposure to H2O2. These speciation details shown using ESI-MS have not yet been described using other techniques. It was concluded that both the apo-MT structure and the metal-loading status impact MT’s metallation and oxidation properties, which provides insight into the structure-function relationship of MTs.