Complex III of Electron Transport Chain: Difference between revisions

Each cytochrome b contains<scene name='Complex_III_of_Electron_Transport_Chain/Hem_cyto_b/5'> two hemes</scene> (displayed as spacefill and colored cpk). Identify each of the hemes by toggling off the spin and hovering the curser over an atom of the heme.  Hem 501 and Hem 502 are in one cytochrome b, and Hem 521 and Hem 522 are in the other one.  The two hemes in each cytochrome b are in different environments and therefore have different properties, e.g. reduction potential. Hemes 501 & 521 have a lower potential than the other two and are called b_L for low potential, and the other two are called b_H for high potential. Each of the cytochrome b's have two binding sites for substrate. [http://en.wikipedia.org/wiki/Ubiquinol Ubiquinol] and the inhibitor stigmatellin bind at one of these sites, Q_P, (<font color='red'>Stigmatellin</font> is shown in the applet below.<ref>The structure shown in the second applet was produced by modifying 1KYO.pdb. The Jmol command 'write file' was used to make a PDB file that contained only the 6 active subunits and cytochrome c (chains c,d,e,n,o,p,w) and the cofactors of those peptides.</ref>), and the site is adjacent to the b_L heme (<scene name='Complex_III_of_Electron_Transport_Chain/Stigmatellin/1' target='second'>return to view of the stigmatellin</scene>). The other site, Q_N, binds [[Coenzyme_Q10|ubiquinone]], and this site is outlined by <scene name='Complex_III_of_Electron_Transport_Chain/Surface_antimycin/1' target='second'>a surface with pockets</scene> which is located adjacent to the b_H heme.  In this view you are looking into the lit pocket in which the ubiquinone binds. You can rotate the structure and observe the ubiquinone binding pocket in the other subunit.