ISSN:
1432-072X
Keywords:
Cytochrome aa 3
;
Cytochrome P450
;
Respiratory chain
;
Streptomyces clavuligerus
;
Oxygen uptake
;
CO-reacting haemoproteins
;
Oxygen metabolism
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The nature of the carbon monoxide- and oxygen-reacting haemoproteins in the respiratory chain of the filamentous antibiotic-producing bacterium Streptomyces clavuligerus has been investigated. CO-difference (i.e. CO+ reduced minus reduced) spectra of intact cells showed the presence of cytochrome aa 3, a CO binding b-type cytochrome, and a pigment resembling cytochrome d. In addition, cells that were approaching the end of the growth phase showed the presence of cytochrome P450: this pigment was undetectable in cells harvested early in the growth cycle. High speed centrifugation of cell-free extracts prepared from cells broken by sonication showed that cytochrome aa 3 was tightly membrane-bound and that cytochrome P450 was soluble. Inhibition of oxygen uptake rates of cells by cyanide indicated that one component, which showed 50% inhibition at 2–4 mM CN−, was acting as major terminal oxidase: this was observed in cells harvested from all stages of growth. Photodissociation (i. e. photolysed, CO reduced minus CO reduced) spectra at-118°C, in the absence of oxygen, showed cytochrome aa 3 to be the sole photolysable CO-reacting haemoprotein. At higher temperature (-87°C), in the presence of oxygen, cytochrome aa 3 formed a complex with oxygen that could not be photolysed by similar intensities of light. By raising the temperature to-43°C, the oxidation of c-type cytochromes was observed. It is concluded that cytochrome aa 3 is the predominant terminal oxidase in S. clavuligerus and that the other CO reacting haemoproteins, of unknown function, are unlikely to be oxidases.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00422288
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