Complex III of Electron Transport Chain: Difference between revisions

<applet load='1kyo' size='400' color='black' frame='true' align='right' scene ='Complex_III_of_Electron_Transport_Chain/Sma_cyto_b1/2' name='second'/>Each <font color='#0000CD'>cytochrome c1</font> contains <scene name='Complex_III_of_Electron_Transport_Chain/Hem_cyto_c1/4'>a heme</scene>. Viewing <scene name='Complex_III_of_Electron_Transport_Chain/Hem_cyto_c1_top/3' target='second'>cyto c1 in spacefill</scene> as it would be seen from the intermembrane space, there is an opening in the center of the dimeric c1 through which one can see the gray hemes of the cyto b's. Also seen in this view is the gray heme embedded in each of the cyto c1's showing that the heme is located in a crevice which is open to the intermembrane space and to the <scene name='Complex_III_of_Electron_Transport_Chain/Hem_cyto_c1_side_open/2'>side facing the Rieske protein</scene> (heme oxygens are seen). These openings of the crevice permits the cyto c1 heme to make contact with the Rieske protein and with cytochrome c when it binds to the <scene name='Complex_III_of_Electron_Transport_Chain/Hem_cyto_c1_top/3'>surface of cyto c1</scene>. There are <scene name='Complex_III_of_Electron_Transport_Chain/Hem_cyto_c1_neg_res/2'>negatively charged acidic residues</scene> which attrack the complementary positive charges on cytochrome c, a basic protein. <scene name='Complex_III_of_Electron_Transport_Chain/Cyto_c_2/1'>Cytochrome c</scene> <font color='cyan'>(colored cyan)</font> bound to one cyto c1 as viewed from intermembrane space and from slice through membrane <scene name='Complex_III_of_Electron_Transport_Chain/Hem_cyto_c/4'>showing that the hemes</scene> of the two cytochromes are in close contact.  The <scene name='Complex_III_of_Electron_Transport_Chain/Hem_cyto_c_transparent/2'>two hemes</scene> seen through transparent spacefill.

<scene name='Complex_III_of_Electron_Transport_Chain/Fes/3'>Fe/S center</scene> is in the head  of each <font color='red'>Rieske protein</font>. Each of the Fe/S centers is complexed with <scene name='Complex_III_of_Electron_Transport_Chain/Fes_his/2'>two His</scene>. As a result of bending at the <scene name='Complex_III_of_Electron_Transport_Chain/Fes_hinge/3'>hinge region</scene> (colored cyan) the head can be in one of three possible positions.  Here the Fe/S head is in the <scene name='Complex_III_of_Electron_Transport_Chain/Fes_his_sma525/2'>cyto b position</scene> in which a His of the Fe/S/His complex is in contact with the ubiquinol (actually <font color='red'>stigmatellin</font> in this model) bound at the Q_P site of cyto b. Wider view of <scene name='Complex_III_of_Electron_Transport_Chain/Fes_posit_cytob/6'>cyto b position</scene>. Make a mental snap shot of how close the Risieke head and Fe/S center is to cyto b and Q_P site in order to compare it to the next scene. The <scene name='Complex_III_of_Electron_Transport_Chain/Load_1bgy/3'>Int position</scene> is intermediate between the other two positions. This view is generating by 1BGY.pdb and takes longer to load since a new pdb file is loading, and it does not have stigmatellin bound at Q_P, so the Rieske protein is in an intermediate position which is not as close to cyto b. The <scene name='Complex_III_of_Electron_Transport_Chain/Fes_posit_c1_arrow/1'>third position</scene> is the Cyto c1 position in which the Fe/S contacts the cyto c1 heme through the second His which is hydrogen bonded to a carboxylate oxygen of the heme in c1 (Black arrow indicates the direction of  movement from Int position to the Cyto c1 position, and the orange arrow indicates the direction of movement from the Int position to the Cyto b position.