Josh Vermaas (Michigan State University): Atomically Resolved Fluxes Across Protein Shells in Photosynthesis and Beyond

Speaker: Josh Vermaas, Michigan State University

Host: Jeffery Klauda

Abstract: Bacterial microcompartments (BMCs) are self-assembling organelles that consist of an enzymatic core that is encapsulated by a selectively permeable protein shell. The enzymatic cores can fulfill multiple functions. Carboxysomes in cyanobacteria are a specific BMC that is responsible for the key carbon fixation in autotrophs. However, bacteria also encapsulate oxygen-sensitive enzymes or reaction pathways with toxic intermediates. Through molecular simulation, we are quantifying the transport and permeation for reactants and products across these protein shells. For photosynthetic metabolites, we find that the permeation rates are all near 0.01 cm/s, near the theoretical optimum rate determined by prior modeling studies. While carbon dioxide is permeable through the carboxysome, we find through atomic-resolution Brownian dynamics simulations that carbon dioxide created in the carboxysome is around 3000 times more likely to be incorporated into the Calvin cycle as it is to leave the carboxysome. Thus, while carboxysomes are technically leaky, carboxysomes overall are highly efficient at maximizing enzymatic catalysis. Harnessing these same design principles, we extend our simulations other metabolites to develop general design principles for BMC engineering for tailored catalysis and metabolism. We find that BMC components are similar in structure when arranged as a sheet or as a spherical particle, and detail the barriers to permeation along the pores within a BMC.

Seminars start at 4:00 pm, and refreshments will be served at 3:45 pm. All seminars are held in the Conference Room (1116) of the Institute for Physical Science and Technology (IPST) Building unless otherwise noted.