RESUMEN
The Arc (anoxic redox control) two-component signal transduction system of Escherichia coli, which comprises the tripartite ArcB sensor kinase and the ArcA response regulator, modulates the expression of numerous operons in response to redox conditions of growth. We demonstrate that the arcA and arcB genes of Haemophilus influenzae specify a two-component system. The Arc proteins of the two bacterial species sufficiently resemble each other that they can participate in heterologous transphosphorylation in vitro. Moreover, the Arc system of H. influenzae mediates transcriptional control according to the redox condition of growth both autologously in its own host and homologously in E. coli, indicating a high degree of functional conservation of the signal transduction system. The H. influenzae ArcB, however, lacks the PAS domain present in the region of E. coli ArcB linking the transmembrane to the cytosolic catalytic domains. Because the PAS domain participates in signal reception in a variety of sensory proteins, including sensors of molecular oxygen and redox state, a similar role was previously ascribed to it in ArcB. Our results demonstrate that the ArcB protein of H. influenzae mediates signal transduction in response to redox conditions of growth despite the absence of the PAS domain.
Asunto(s)
Proteínas de Escherichia coli , Haemophilus influenzae/metabolismo , Proteínas de la Membrana/metabolismo , Proteínas Quinasas/metabolismo , Proteínas Represoras , Secuencia de Aminoácidos , Proteínas de la Membrana Bacteriana Externa/metabolismo , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Escherichia coli/genética , Regulación Bacteriana de la Expresión Génica , Prueba de Complementación Genética , Haemophilus influenzae/genética , Proteínas de la Membrana/genética , Datos de Secuencia Molecular , Mutación , Oxidación-Reducción , Fosforilación , Proteínas Quinasas/genética , Estructura Terciaria de Proteína , Homología de Secuencia de Aminoácido , Transducción de SeñalRESUMEN
PIP: A sesquiterpene lactone given the trivial name leucanthanolide, from the Mexican zoapatle plant (Montanoa leucantha), long used as an herbal remedy, was isolated and was found to have cytotoxicity but no uterine activity. The compound was isolated from the fraction containing zoapatanol, a substance being investigated for its ability to induce menses, abortion and labor. The compound has a molecular formula of C19H2606, a 5-membered lactone ring, an ester group, and a germacradienolide skeleton. It was evaluated for abortifacient activity in pregnant guinea pigs by intraperitoneal injection on day 22 of gestation. 3 of 5 animals had abnormal fetuses, but there was no evidence of early uterine activity. Cytotoxic testing in vitro was done on KB and P-388 test systems in cell culture. The ED50 of leucanthanolide was 0.57 mcg/ml (KB) and 0.93 (P-388). In comparison, the ethyl acetate fraction had an ED50 of 1.35 mcg/ml and 5.2 mcg/ml respectively.^ieng