Speaker: Ditlev Egeskov Brodersen
Bacterial pathogens regulate gene expression of virulence factors in response to environmental stimuli, including nutrient starvation. The PhoR/PhoB two-component regulatory system plays a key role in the response to low extracellular phosphate concentrations and results in induction of a set of genes known as the Pho regulon. In E. coli, the Pho regulon includes the 14-cistron phn operon, which encodes the C-P lyase pathway that allows for utilisation of phosphonate compounds for growth. Phosphonates that are characterised by the highly stable C-P bond, are widespread in nature but are also used as antibiotics due to their ability to mimic phosphate esters.
Despite the potential medical relevance and industrial applications of the C-P lyase pathway, the underlying molecular details of the process are still relatively poorly understood, mainly because of the complexity and the fact that the enzyme requires anaerobic conditions. In our lab, we use biochemistry and structural biology to dissect the architecture and mechanism of E. coli C-P lyase. We can show that the PhnJ subunit of the PhnGHIJ core complex, which catalyses a key step in the phosphonate breakdown pathway, mediates binding of a unique dual dimer of the non-transporter ATP-binding cassette (ABC) subunits, PhnK and PhnL. Using single-particle electron cryo-microscopy, we determine the structure of the 340 kDa PhnGHIJKL complex in several functional states, revealing dimer of PhnK in an ATP-bound closed state interacting with both PhnJ and a dimer of PhnL, which is in an open ADP-like state. Structural analysis under ATP turnover conditions further reveals that hydrolysis of ATP induces a remodelling of the core complex via a transition similar to that observed for ABC transporters. We believe these results have wide-ranging implications for our understanding of natural breakdown of phosphonates and more generally, the role of ABC modules in biological systems.
Seweryn, P., Van, L.B., Kjeldgaard, M., Russo, C.J., Passmore, L.A., Hove-Jensen, B., Jochimsen, B., and Brodersen, D.E. (2015). Nature 525, 68-72. Link
Manav, M.C., Sofos, N., Hove-Jensen, B., and Brodersen, D.E. (2018). Bioessays 40, e1800091. Link
Amstrup, S.K., Ong, S.C., Sofos, N., Karlsen, J.L., Skjerning, R.B., Boesen, T., Enghild, J.J., Hove-Jensen, B., and Brodersen, D.E. (2023). Nat Commun 14, 1001. Link