New structural evidence shows that the cyanobacterial protein CcmM (orange) binds to fully assembled RuBisCo enzymes (yellow and green) without dislodging RbcS subunits (yellow).
This crosslinked mixture forms the basis of the carboxysome, a compartment bacteria use to avoid photorespiration. Photorespiration is a wasteful step in photosynthesis caused when RuBisCo fixes oxygen instead of carbon dioxide, and is thought to reduce the yield of some crops by over 20%. By trapping carbon dioxide in carboxysomes, bacteria increase its concentration, helping RuBisCo correctly fix CO2. Greater insight into carboxysome assembly may help engineer higher-yield crops in the near future.
This research appears in the Journal of Biological Chemistry.