Cofactor uptake in 1,2-propanediol metabolising microcompartments

Mayer, Matthias, Frank, Stefanie, Deery, Evelyne, Lawrence, Andrew, Smales, Mark and Warren, Martin (2014) Cofactor uptake in 1,2-propanediol metabolising microcompartments. New Biotechnology, 31, S22-S23. (doi:10.1016/j.nbt.2014.05.1663).

Abstract

Propanediol utilising microcompartments are proteinaceous structures consisting of a shell that incorporates enzymes necessary for 1,2-propanediol degradation. The shell is formed by 7 different types of proteins that form hexamers (assemble to form the faces of the shell) or pentamers (vertices of the shell) with central pores and is thought to protect the cell from the toxic propionaldehyde intermediate as well as to transport substrate and cofactors across the protein shell. The dehydration of 1,2-propanediol to propionaldehyde, which is catalysed by the protein complex PduCDE, is B12 (adenosylcobalamin) dependent. Previously it was shown that the pdu microcompartment houses enzymes to regenerate B12. Uptake of B12 into enteric cells and reactivation are well described, but it still remains unclear if B12 is transported or accumulated inside Pdu microcompartments.

We investigated if Pdu microcompartments take up or accumulate B12. Recombinantly expressed and purified empty microcompartments (shell proteins) and full Pdu microcompartments (fully expressed pdu operon) showed a higher content of B12 than the crude cell lysate, suggesting that Pdu microcompartments have an inherent ability to bind and gather B12. Different cobalamins were found to be co-purified with both the empty and the fully expressed microcompartments. This finding was confirmed by in vitro co-localisation studies of purified microcompartments with fluorescently labelled B12. The uptake mechanism remains unclear and is part of our current research.

An understanding of transport along the protein shell and its selectivity is an important landmark in our efforts to generate engineered compartments capable of sequestering complex synthetic metabolic pathways.

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Contributors

Author: Andrew Lawrence

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