The cytochrome bc1 is one of the three major respiratory enzyme complexes residing in the inner mitochondrial membrane. Cytochrome bc1 transfers electrons from ubiquinol to cytochrome c and uses the energy thus released to form an electrochemical gradient across the inner membrane. Our X-ray crystal structures of the complex from chicken, cow and rabbit in both the presence and absence of inhibitors of quinone oxidation, reveal two different locations for the extrinsic domain of one component of the enzyme, an iron-sulphur protein. One location is close enough to the supposed quinol oxidation site to allow reduction of the Fe-S protein by ubiquinol. The other site is close enough to cytochrome c1 to allow oxidation of the Fe-S protein by the cytochrome. As neither location will allow both reactions to proceed at a suitable rate, the reaction mechanism must involve movement of the extrinsic domain of the Fe-S component in order to shuttle electrons from ubiquinol to cytochrome c1. Such a mechanism has not previously been observed in redox protein complexes.

Electron transfer by domain movement in cytochrome bc1.

Selective Targeting of a Redox-active Ubiquinone to Mitochondria within Cells: ANTIOXIDANT AND ANTIAPOPTOTIC PROPERTIES *

https://deepblue.lib.umich.edu/bitstream/2027.42/30145/1/0000522.pdf

Cardiolipins and biomembrane function

https://patofyziologie.lf1.cuni.cz/file/103/Clear%20native%20electrophoresis.pdf

High Resolution Clear Native Electrophoresis for In-gel Functional Assays and Fluorescence Studies of Membrane Protein Complexes

Primary structure and subunit stoichiometry of F1-ATPase from bovine mitochondria

Publisher Summary This chapter investigates the preparation, properties, and conditions for assay of mitochondria. Three procedures are described for the isolation of mitochondria from slaughterhouse material. These procedures for the isolation of beef heart mitochondria differ only in the manner in which the heart mince is homogenized. The fractionation of the mitochondria and washing steps are the same in the three procedures. Procedure 1 dislodges the loosely packed damaged mitochondria, and the mixture is decanted and discarded. A portion of the light beef heart mitochondria (LBHM) adheres to the wall of the centrifuge tube, and it can be removed with the aid of a glass-stirring rod. Procedure 2 involves the use of a proteolytic enzyme to aid in the homogenization of the heart mince, and has the advantage of producing a higher yield of mitochondria than the first procedure. Mitochondria prepared by this procedure manifest higher respiratory control ratios. Procedure 3 leads to the formation of a large proportion of damaged mitochondria (LBHM) but has the advantage that large amounts of material can be worked up at one time. This method uses a Waring blendor to homogenize the heart mince. Mitochondria that are prepared and assayed with distilled water that had been passed through two ion exchange beds consistently exhibit P : O ratios greater than 3 for pyruvate, β-hydroxybutarate, α-ketoglutarate and greater than 2 for succinate.

Archie L. Smith

Papers

[13] Preparation, properties, and conditions for assay of mitochondria: Slaughterhouse material, small-scale