Metal ions and protein folding: conformational and functional interplay

Dissertation presented to obtain a PhD degree in Biochemistry at Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa

Metal ions are cofactors in about 30% of all proteins, where they fulfill catalytical and structural roles. Due to their unique chemistry and coordination properties they effectively expand the intrinsic polypeptide properties (by participating in catalysis or electron transfer reactions), stabilize protein conformations (like in zinc fingers) and mediate signal transduction (by promoting functionally relevant protein conformational changes). However, metal ions can also exert have deleterious effects in living systems by incorporating in non-native binding sites, promoting aberrant protein aggregation or mediating redox cycling with generation of reactive oxygen and nitrogen species. For this reason, the characterization of the roles of metal ions as modulators of protein conformation and stability provides fundamental knowledge on protein folding properties and is instrumental in establishing the molecular basis of disease. In this thesis we have analyzed protein folding processes using model protein systems incorporating covalently bound metal cofactors – iron-sulfur (FeS) proteins – or where metal ion binding is reversible and associated conformational readjustments – the S100 proteins.(...)