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“Green carbon capture”: Towards a mechanistic understanding of how photosynthetic bacteria transport and store CO2.

Primary Supervisor: Professor Alex Cameron, School of Life Sciences

Secondary supervisor: Dr Richard Puxty, Prof Dave Scanlan

PhD project title: “Green carbon capture”: Towards a mechanistic understanding of how photosynthetic bacteria transport and store CO2.

University of Registration: University of Warwick

Project outline:

Membrane transport proteins enable small molecules such as nutrients, ions, neurotransmitters, and toxins to move across cellular membranes. This project centres on transporters that drive the uptake of bicarbonate. Bicarbonate transporters are widespread throughout the evolutionary scale. In humans, in concert with carbonic anhydrase, human anion exchanger 1, removes toxic CO2from red blood cells. Meanwhile, in cyanobacteria, they are responsible for the acquisition of CO2 from the environment to drive photosynthesis.

These cyanobacteria are responsible for about a quarter of photosynthesis on Earth, partly facilitated by a sophisticated mechanism to transport and concentrate CO2around the most active form of RuBisCO in nature. This carbon concentrating mechanism (CCM) involves locally increasing CO2in a small proteinaceous microcompartment called the carboxysome, which also houses the RuBisCO. In essence, cyanobacteria act as nature’s very own green carbon capture and storage system. So efficient is the CCM, that transgenic expression of the machinery is predicted to significantly boost agricultural yields by overcoming the frailties of plant RuBisCO. However, for this to be realized, a fundamental understanding of how CO2(in the form of bicarbonate) enters the cell in the first instance.

The fundamental goal of this project is to understand the mechanism of bicarbonate transporters from cyanobacteria through the use of X-ray crystallography in conjunction with biochemical experiments. The transporters of interest are sodium-coupled secondary transporters. We wish to understand how the sodium gradient drives the conformational changes that are necessary to transport the bicarbonate across the membrane. The impact of the project will be seen in contributing to understanding the mechanism of the CCM, toward the aim of engineering crops for increased capacity for photosynthesis.

Relevant papers to the work in the lab, using crystallography to understand protein mechanism:

  1. Alguel, Y., et al., Structure of eukaryotic purine/H(+) symporter UapA suggests a role for homodimerization in transport activity.Nat Commun, 2016. 7: p. 11336.
  2. Arakawa, T., et al., Crystal structure of the anion exchanger domain of human erythrocyte band 3.Science, 2015. 350(6261): p. 680-4.
  3. Shimamura, T., et al., Molecular basis of alternating access membrane transport by the sodium-hydantoin transporter Mhp1.Science, 2010. 328(5977): p. 470-473.

BBSRC Strategic Research Priority: Understanding the Rules of Life: Structural biology

    Techniques that will be undertaken during the project:

    • Molecular Biology
    • Growth of Bacterial Cultures
    • Protein Crystallisation, X-ray data collection and Structure Solution
    • Biochemical Assays

    Contact: Professor Alex Cameron, University of Warwick