Cytochrome bd-I in Escherichia coli is less sensitive than cytochromes bd-II or bo'' to inhibition by the carbon monoxide-releasing molecule, CORM-3: N-acetylcysteine reduces CO-RM uptake and inhibition of respiration.
Biochim Biophys Acta
; 1834(9): 1693-703, 2013 Sep.
Article
em En
| MEDLINE
| ID: mdl-23624261
ABSTRACT
BACKGROUND:
CO-releasing molecules (CO-RMs) are potential therapeutic agents, able to deliver CO - a critical gasotransmitter - in biological environments. CO-RMs are also effective antimicrobial agents; although the mechanisms of action are poorly defined, haem-containing terminal oxidases are primary targets. Nevertheless, it is clear from several studies that the effects of CO-RMs on biological systems are frequently not adequately explained by the release of CO CO-RMs are generally more potent inhibitors than is CO gas and other effects of the molecules are evident.METHODS:
Because sensitivity to CO-RMs cannot be predicted by sensitivity to CO gas, we assess the differential susceptibilities of strains, each expressing only one of the three terminal oxidases of E. coli - cytochrome bd-I, cytochrome bd-II and cytochrome bo', to inhibition by CORM-3. We present the first sensitive measurement of the oxygen affinity of cytochrome bd-II (Km 0.24µM) employing globin deoxygenation. Finally, we investigate the way(s) in which thiol compounds abolish the inhibitory effects of CORM-2 and CORM-3 on respiration, growth and viability, a phenomenon that is well documented, but poorly understood.RESULTS:
We show that a strain expressing cytochrome bd-I as the sole oxidase is least susceptible to inhibition by CORM-3 in its growth and respiration of both intact cells and membranes. Growth studies show that cytochrome bd-II has similar CORM-3 sensitivity to cytochrome bo'. Cytochromes bo' and bd-II also have considerably lower affinities for oxygen than bd-I. We show that the ability of N-acetylcysteine to abrogate the toxic effects of CO-RMs is not attributable to its antioxidant effects, or prevention of CO targeting to the oxidases, but may be largely due to the inhibition of CO-RM uptake by bacterial cells.CONCLUSIONS:
A strain expressing cytochrome bd-I as the sole terminal oxidase is least susceptible to inhibition by CORM-3. N-acetylcysteine is a potent inhibitor of CO-RM uptake by E. coli. GENERALSIGNIFICANCE:
Rational design and exploitation of CO-RMs require a fundamental understanding of their activity. CO and CO-RMs have multifaceted effects on mammalian and microbial cells; here we show that the quinol oxidases of E. coli are differentially sensitive to CORM-3. This article is part of a Special Issue entitled Oxygen Binding and Sensing Proteins.Palavras-chave
(2'7'-diacetate); ([Ru(CO)(3)Cl(2)](2)); CO-RM; CORM-2; CORM-3; Cytochrome; DCFH-DA; EDTA; EGTA; Escherichia coli; HO-1; ICP-MS; K(L)a; K(d); K(m); LB; Luria Bertani broth; Michaelis constant, the concentration of substrate that gives half-maximal velocity; N-acetylcysteine; NAC; PBS; ROS; Respiratory oxidase; Ru(CO)(3)Cl(glycinate); SOD; V(max); carbon monoxide-releasing molecule; dissociation constant; ethylene diamine tetraacetic acid; ethylene glycol tetraacetic acid; gas transfer (gas to liquid) coefficient; haem oxygenase-1; iCORM-3; inactive CORM-3; inductively coupled plasma mass spectrometry; maximal rate; miCORM-3; myoglobin-inactivated CORM-3; phosphate-buffered saline; reactive oxygen species; superoxide dismutase
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Compostos Organometálicos
/
Oxirredutases
/
Consumo de Oxigênio
/
Acetilcisteína
/
Monóxido de Carbono
/
Respiração Celular
/
Citocromos
/
Proteínas de Escherichia coli
/
Complexo de Proteínas da Cadeia de Transporte de Elétrons
/
Escherichia coli
Tipo de estudo:
Diagnostic_studies
Idioma:
En
Revista:
Biochim Biophys Acta
Ano de publicação:
2013
Tipo de documento:
Article
País de afiliação:
Reino Unido