Figure 5. RubisCO activity in cell extracts of the cbbL::Tc NC cbbL, cbbLS::Tc NC cbbLS, and cbbLS::kan^r mutants.

Clarified extracts of H. neapolitanus cbbL::Tc NC cbbL (A), cbbLS::Tc NC cbbLS (B), and cbbLS::kan^r (C) mutant cells were separated on 0.2–0.8 M sucrose gradients. The resulting fractions were assayed for RubisCO activity (cpm) and protein content (mg/ml). Aliquots (25 µl) of fractions 16–30 were probed for the presence of CbbL and CbbM with antibodies specific for each RubisCO type. L = 5 µg of clarified cell extract prior to gradient centrifugation; (+) = wild type carboxysome control.