Genetic and biochemical characterization of protein complexes that are essential for bacterial chromosome segregation and maintenance

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Protein-protein interactions (molecular "handshakes") are crucial for the operation and function of all living organisms. These interaction interface are often formed by a subset of key amino acid residues from each protein partner. Interfacial residues often vary between orthologs, indicating some degree of mutability or degeneracy. But it is unclear how plastic the interface is and how the combination of key amino acid residues at the interface supports a robust and specific protein-protein interaction. This DTP PhD project aims to comprehensively characterise the sequence space around an ancestral protein ParB that is crucial for bacterial chromosome segregation. The student will:(i) characterise the effect on functions of all possible mutations and combination of mutations at a subset of amino acids that are crucial for ParB-ParB interaction by saturated mutagenesis and deep sequencing.(ii) validate the functionality of the identified ParB variants by a combination of in vitro and in vivo techniques.(ii) project the mutational sequence space on to the three-dimensional structure of ParB to fully characterise the sequence-structure-function relationship. We use the Caulobacter crescentus chromosome partitioning protein B (ParB) as an ideal model system for this project.