Structure of a beta ring of the yeast proteasome. The included threonine protease subunits are inhibited by salinosporamide. These threonine protease subunits belong to the PB clan, also known as "N-terminal nucleophile" clan, since the side chain of the first residue of the mature enzyme provides the nucleophile which attacks the target peptidic bond. The nitrogen atom in the backbone of this first residue is also believed to participate in the catalysis by accepting a proton from the substrate and later donating a proton to the leaving peptide.
Structures are rendered as ribbons. Catalytic and catalytic metal-complexing residues are shown as neons. Inhibitors are displayed as space filling spheres.
Carbons are shown in light gray, hydrogens in cyan, oxygens in red, nitrogens in blue, and sulfurs in yellow.
Left-click and drag to rotate the protease. Right-click and drag up/down to zoom in/out. Click with both buttons and drag to move the protease. Use the upper bar to get different views and for display options. For a close-up of the catalytic site, choose the cat_site view.
Once you have clicked inside the structure window, you can use the keyboard to hide/show objects:
'1' toggles the ribbon. '2' toggles the inhibitor. '3' toggles the catalytic residues.