Polyhedric features of cysteine: from protein functionalization to copper-binding

Abstract

This thesis comprises two main projects which are about the cysteine chemistry involved in protein functionalization and copperbinding. Plastocyanin functionalization via cysteine has been used to produce a conjugate for the aim of obtaining structural information of a self-assembled state directed by the conjugation. This aim was achieved with a PEGylated Plastocyanin by using NMR spectroscopy and X-ray crystallography. The first crystal structure of a PEGylated protein has been solved at a resolution of 4.2 Å. The electron density of the PEG chain is not visible suggesting a highly disordered structure, but the crystal packing is remarkable: a right-handed antiparallel double-helical assembly was observed. In biological systems cysteine can be coordinated to copper, an essential trace element which is associated with neurodegenerative disorders and therefore its trafficking is regulated in cells. The preliminary NMR study of a novel cysteine rich copper-binding protein found by the group of Prof. Dennison in Newcastle University (UK) is presented. 15N-, 13C15N- and 15N-selective amino acid labelled protein samples were produced to assign the backbone resonances and to study the binding of copper.