Fig. 5.

Model of CbbQO function. The VWA domain of the Rca’s CbbO adaptor protein engages the acidic surface residue E75 of the inhibited Rubisco. Rubisco binding results in a signal which originates at the VWA domain and is transferred toward the CbbQ active sites to release the suppressed ATPase activity. Both L161 (β4-α4 loop) and L85 are involved in signal transmission. L85 is likely involved in force transmission from the hexamer to the CbbO adaptor, which will remodel the inhibited Rubisco to trigger active site opening and inhibitor release. The Q2O2 model is an overlay of the EM reconstruction and the AfQ2 crystal structure shown in ribbon representation. L161 (red) and L85 (magenta) are shown as spheres. Rubisco is a surface representation of the hexameric Rhodopseudomonas palustris form II Rubisco (PDB ID code 4lf1).