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bioRxiv · 10.1101/2020.06.26.173062

Calculating metalation in cells reveals CobW acquires CoII for vitamin B12 biosynthesis upon binding nucleotide

Young, T. R.·Martini, M. A.·Osman, D.·Morton, R. J.·Deery, E.·Warren, M. J.·Robinson, N. J.
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Abstract

Protein metal-occupancy (metalation) in vivo has been elusive. Here we develop a metalation-calculator which accounts for inter-metal competition and changing metal-availabilities inside cells. The calculations are based on available free-energies of metals determined from the responses of metal sensors. We use the calculator to understand the function and mechanism of CobW, a predicted CoII-chaperone for vitamin B12. CobW is calculated to acquire negligible metal alone: But, upon binding nucleotide (GTP) and MgII, CobW assembles a high-affinity site that can obtain CoII or ZnII from the intracellular milieu. In idealised cells with sensors at the mid-points of their responses, competition within the cytosol enables CoII to outcompete ZnII for binding CobW. Thus, CoII is the cognate metal. However, after growth in different [CoII], CoII-occupancy ranges from 10 to 97% which matches CobW-dependent B12 synthesis. The calculator reveals how CobW acquires its metal and is made available for use with other proteins.

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Young, T. R., Martini, M. A., Osman, D., Morton, R. J., Deery, E., Warren, M. J., Robinson, N. J.. 2020-06-27. Calculating metalation in cells reveals CobW acquires CoII for vitamin B12 biosynthesis upon binding nucleotide. https://doi.org/10.1101/2020.06.26.173062

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