RESUMEN
Simple urea compounds ("phurealipids") have been identified from the entomopathogenic bacterium Photorhabdus luminescens, and their biosynthesis was elucidated. Very similar analogues of these compounds have been previously developed as inhibitors of juvenile hormone epoxide hydrolase (JHEH), a key enzyme in insect development and growth. Phurealipids also inhibit JHEH, and therefore phurealipids might contribute to bacterial virulence.
Asunto(s)
Productos Biológicos/farmacología , Inhibidores Enzimáticos/farmacología , Epóxido Hidrolasas/antagonistas & inhibidores , Photorhabdus/química , Urea/farmacología , Animales , Productos Biológicos/química , Productos Biológicos/metabolismo , Inhibidores Enzimáticos/química , Inhibidores Enzimáticos/metabolismo , Epóxido Hidrolasas/metabolismo , Insectos , Relación Estructura-Actividad , Urea/análogos & derivados , Urea/metabolismoRESUMEN
Bacterial adhesion on implants is a first step in the development of chronic foreign body associated infections. Finding strategies to minimize bacterial adhesion may contribute to minimize such infections. It is known that surfaces with oligo-ethylene-glycol (EG3OMe) or poly-ethylene-glycol (PEG2k) terminations decrease unspecific protein adsorption and bacterial adhesion. However, little is known about the influence of serum and its components on bacterial adhesion. We therefore prepared two coatings on gold surface with HS-(CH2)11EG3OMe (EG3OMe) and PEG2k-thiol and studied the role of bovine serum albumin (BSA), γ-globulins, and serum on Staphylococcus aureus adhesion. While BSA and lysozyme showed no adherence even when applied at very high concentrations (100 mg/ml), γ-globulins adsorbed already from 10 mg/ml on. The adsorption of γ-globulins was, however, significantly decreased when it was mixed with BSA in a ratio of 3:1, as it is in the serum. Pretreatment of EG3OMe and PEG2k coatings with γ-globulins or serum strongly promoted adherence of S. aureus when resuspended in buffer, suggesting that γ-globulins play a pivotal role in promoting S. aureus adhesion by its IgG binding proteins; the finding that a spa-deletion mutant, lacking the IgG binding protein A, showed decreased adherence corroborated this. Similarly, when S. aureus was pretreated with serum or γ-globulins its adherence was also significantly decreased. Our findings show that particularly γ-globulins bind to the coated surfaces thus mediating adherence of S. aureus via its protein A. As pretreatment of S. aureus with serum or γ-globulins significantly decreased adherence, treatment of patients with γ-globulins before implant surgery might lower the risk of implant-associated infections.
Asunto(s)
Adhesión Bacteriana , Proteínas Sanguíneas/metabolismo , Materiales Biocompatibles Revestidos , Glicol de Etileno/metabolismo , Staphylococcus aureus/fisiología , Propiedades de Superficie , Animales , Bovinos , Humanos , Inmunoglobulina G/metabolismo , Unión Proteica , Proteína Estafilocócica ARESUMEN
Epstein-Barr virus (EBV) expresses two transcription factors, Rta and Zta, which are involved in the transcriptional activation of EBV lytic genes. This study sought to elucidate the mechanism by which Rta activates transcription of the Zta-encoding gene, BZLF1, through the ZII element in the gene promoter. In a DNA affinity precipitation assay, ATF2 was found to associate with an Rta-interacting protein, MCAF1, at the ZII element. The interaction between Rta, MCAF1, and ATF2 at the same site in the ZII region was further verified in vivo by chromatin immunoprecipitation assay. The complex appears to be crucial for the activation of BZLF1 transcription, as the overexpression of two ATF2-dominant negative mutants, or the introduction of MCAF1 siRNA into 293T cells, were both found to substantially reduce Rta-mediated transcription levels of BZLF1. Moreover, this study also found that the Rta-MCAF1-ATF2 complex binds to a typical AP-1 binding sequence on the promoter of BMRF2, a key viral gene for EBV infection. Mutation of this sequence decreased Rta-mediated promoter activity significantly. Taken together, these results indicate a critical role for MCAF1 in AP-1-dependent Rta activation of BZLF1 transcription.
Asunto(s)
Herpesvirus Humano 4/genética , Transactivadores/genética , Factores de Transcripción/metabolismo , Transcripción Genética , Factor de Transcripción Activador 2/química , Factor de Transcripción Activador 2/metabolismo , Sitios de Unión , Línea Celular Tumoral , Humanos , Inmunoprecipitación , Glicoproteínas de Membrana/genética , Regiones Promotoras Genéticas/genética , Unión Proteica , Dominios y Motivos de Interacción de Proteínas , Mapeo de Interacción de Proteínas , Proteínas Represoras , Factor de Transcripción AP-1/metabolismo , Factores de Transcripción/química , Activación Transcripcional/genética , Proteínas Virales/genéticaRESUMEN
The knowledge that many pathogens rely on cell-to-cell communication mechanisms known as quorum sensing, opens a new disease control strategy: quorum quenching. Here we report on one of the rare examples where Gram-positive bacteria, the 'Staphylococcus intermedius group' of zoonotic pathogens, excrete two compounds in millimolar concentrations that suppress the quorum sensing signaling and inhibit the growth of a broad spectrum of Gram-negative beta- and gamma-proteobacteria. These compounds were isolated from Staphylococcus delphini. They represent a new class of quorum quenchers with the chemical formula N-[2-(1H-indol-3-yl)ethyl]-urea and N-(2-phenethyl)-urea, which we named yayurea A and B, respectively. In vitro studies with the N-acyl homoserine lactone (AHL) responding receptor LuxN of V. harveyi indicated that both compounds caused opposite effects on phosphorylation to those caused by AHL. This explains the quorum quenching activity. Staphylococcal strains producing yayurea A and B clearly benefit from an increased competitiveness in a mixed community.