FIG. 3.
Characterization of isolated Φ(gfp-cbbS)(Hyb)::Kanr mutant carboxysomes. (A) Wild-type (left) and mutant (right) carboxysomes were purified by centrifugation through a linear sucrose density gradient. Tyndall scattering of the carboxysome band is evident in both gradients, but only Φ(gfp-cbbS)(Hyb)::Kanr mutant carboxysomes are fluorescent green. (B) Transmission electron micrographs of negatively stained wild-type and mutant carboxysomes do not reveal any obvious morphological differences. Bars, 100 nm. (C) Polypeptide composition of purified wild-type and mutant carboxysomes. Polypeptides were separated by SDS-polyacrylamide gel electrophoresis (the stained gel on the left). The GFP-CbbS fusion protein replaces wild-type CbbS in the mutant carboxysomes. The location of GFP was evident after probing an immunoblot (right) with an anti-GFP antibody.