Model of Cytochrome b from the bc-complex of Rb. sphaeroides.

The model contains six of the eight predicted transmembrane helices (A-F) and putative amphipathic helices at the N-terminal end (a), between helices A and B (ab), and between helices C and D (cd).
Residues shown in blue are those which when mutated give rise to effects (inhibitor resistance, modified kinetics, change in semiquinone stability) at the Qi-site.
Residues shown in orange or yellow are those which when mutated give rise to inhibitor resistance or modified kinetics at the Qo-site.
Ubiquinones are shown to indicate the approximate location of the Qo-site (purple) and the Qi-site (green). The picture was decorated with text using Paint. The coordinates for the model were generated using the Ribosome function from the PSAAM package.

View of Model Structure

Click here for a brief tutorial on the model.

You will need Netscape 2.0 or higher, and Chemscape Chime to see the model within your viewer

You can download Chime by clicking here. Chime plug-in

Cytochrome b viewed from the cytoplasmic side.

Cytochrome b - side view.

Model of cytochrome b displayed using the Render Window of PDVWIN program.

The structure is shown as a stereo pair for crossed-eye viewing. Residues thought to contact the Qi-site are in blue; those at the Qo-site in orange. Ubiquinones are shown to indicate the approximate location of the Qo-site (dark-blue) and the Qi-site (green). The picture was decorated with text using Paint.

Qo-site.

Model of Qo-site.

The side chains of residues around the Qo-site are shown, with positions of predicted helices painted in as transparent cylinders. The residues are depicted in the ball-and-stick representation obtained using the Togl Side Chains On, Togl Backbone off, Highlight residues by number, Circle atoms, and Number residues functions of PDVWIN.

Qi-site.

Model of Qi-site.

The side chains of residues around the Qi-site are shown, with positions of predicted helices painted in as transparent cylinders.