Control of Rate of Intracellular Respiration 69 



with a considerable intensification of the band, while the 

 oxidized form combined with cyanide, with a shift of the band 

 from 410 m(i, to 418 m[ji. They gave the name "mitochrome" 

 to this pigment. 



The action of this mitochrome preparation has been 

 studied by Hiilsmann, Elliott and Rudney (1958) who found 

 that the uncoupling activity could be separated from the 

 haem compound by extraction with isooctane. The uncoupling 

 activity was found quantitatively in the isooctane, while the 

 spectrum of the haem compound (for which the name mito- 

 chrome is retained) was found unchanged in the water layer. 

 The uncoupling activity of the unextracted mitochrome 

 preparation w^as unaffected by the addition of reducing 

 or oxidizing agents, or by the addition of cyanide or CO, 

 which combined wdth mitochrome. Boiling the mitochrome 

 preparation, or precipitation with trichloroacetic acid, did not 

 destroy the uncoupling activity, which was found in the 

 precipitate. 



It is clear, then, that the uncoupling activity of Polls and 

 Shmukler's mitochrome preparation is not due to the haem- 

 protein mitochrome which it contains, but to a component, 

 presumably lipid in nature, which is extractable by organic 

 solvents from this preparation. However, it is possible that 

 the lipid material is more than an accidental contaminant of 

 mitochrome. 



Hiilsmann, Elliott and Rudney (1958) (see also Elliott, 

 Hulsmann and Slater, 1959) found that the spectrum of 

 partially purified preparations of cytochrome (a + Og), con- 

 taining cholate and perhaps hydrolytic enzymes, changed to 

 that of mitochrome after standing at 4° for a few days. A 

 preparation of cytochrome b (containing some cytochrome q) 

 behaved in the same way. These- preparations of cytochrome 

 (a + ag) and of cytochrome b which had turned into mito- 

 chrome yielded an isooctane extract with the same properties 

 as the lipid extracted from Polls and Shmukler's mitochrome 

 preparation. The original cytochrome preparations yielded 

 much less of this uncoupling material (Table III). 



