Summary: Optical changes in and -type cytochromes, following initiation of the reaction of cytochrome oxidase with O, have been studied in cells and derived membrane particles from oxygen-limited cultures of K12. At successively higher temperatures between — 132 and — 88 °C, the first scan after photolysis of the CO-liganded, reduced oxidase in the presence of O shows a diminution of cytochrome (believed to be an early intermediate in the O reaction) and a slow increase in absorbance at 675 to 680 nm due to an unidentified chromophore. A similar sequence occurs when a single sample is scanned repetitively at — 91 °C. At higher temperatures, oxidation of at least two spectrally distinct cytochromes occurs. Selective photolysis of the cytochrome -CO complex with a He-Ne laser shows that neither of these cytochromes is the CO-binding cytochrome . In all oxidation states examined, no absorbance in the 720 to 860 nm region was observed; it is concluded that both cytochromes and lack redox-active copper that has an environment similar to the copper(s) in mitochondrial cytochrome oxidase.

The amount of cytochrome (but not the amount of reduced cytochrome ) formed after photolysis is directly proportional to the oxygen concentration in the sample at the time of freeze trapping. The results are discussed in relation to the composition and mechanism of action of cytochrome


Article metrics loading...

Loading full text...

Full text loading...


Most cited this month

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error