Streptococcus pneumoniae is the world’s foremost bacterial pathogen. Globally, disease burden from S. pneumoniae accounts for more childhood deaths than AIDS, malaria and tuberculosis combined every year 1. Essential to the survival of all organisms is the first-row transition metal ion zinc. S. pneumoniae scavenges zinc from the host environment in order to mediate colonization and disease. However, recent studies have also shown that zinc has potent antimicrobial activity at high concentrations. In order to evade zinc toxicity, S. pneumoniae has to be able to efflux excess zinc, an action attributed to the integral membrane protein CzcD.
Here my work sought to understand how zinc homeostasis is achieved in S. pneumoniae via the structural and functional characterization of CzcD. This includes the determination of the structure of CzcD via X-ray crystallography to define the three-dimensional architecture of the protein and determination of the affinity of the protein for zinc. This study outlines progress made towards the characterisation of CzcD by X-ray crystallography, including the development of a protocol for the over-expression, purification and crystallisation of the protein as well as preliminary zinc binding analyses.