Synthetic biology approaches to construct metal analogues of vitamin B12 to act as anti-microbial and imaging agents for health applications.

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Vitamin B12 (cobalamin) is an essential micronutrient whose synthesis is restricted to only certain bacteria. It is one of the most complex molecules found in Nature, consisting of a cobalt-containing corrin ring and a lower base attached via the nucleotide loop. The biological activity of the molecule is dependent on the properties of the metal ion at its centre.We have successfully prepared several metal analogues of cobalamin (Rh, Zn and Ni). This was achieved using a novel approach consisting of an engineered bacterial strain which can produce a metal-free intermediate, hydrogenobyric acid (Hby), and then subsequent biochemical and chemical steps to complete the synthesis and produce the desired analogues. While the system works well, we are looking to optomise/simplify the synthesis by further engineering the E. coli strain, using genes from Chromatium vinosum which is known to produce cobalt-free cobalamin under specific conditions.We have determined that the rhodium analogue is an inhibitor of B12-dependent processes, but we currently know very little about the biological activity of the metal analogues. We wish to expand our knowledge in this area by looking at the cellular uptake and trafficking of the analogues, their effect on B12-dependent enzymes and processes, and document any antimicrobial/anticancer activity present. The ability to replace the metal ion also opens the possibility of creating unique medical imaging agents for positron emission tomography (PET) which could be used in cancer diagnosis.The aim of this project is to:1. Synthesise a range of metal analogues of cobalamin (Cu, Rh, Zn and Ni).2. Investigate the biological properties of the metal analogues (eg. vitamin uptake/transport, enzyme inhibition, antimicrobial/anticancer agents).3. Engineer an E. coli strain capable of producing cobalt-free cobalamin (hydrogenobalamin).