RESUMEN
To determine the relationship of human herpesvirus-6 (HHV-6) infection to febrile convulsions, cerebrospinal fluid (CSF) from patients with a history of febrile convulsion were tested by polymerase chain reaction (PCR) amplification for HHV-6 DNA. HHV-6 DNA was detected in 9 of 10 samples from patients with exanthem subitum who showed neurologic symptoms. Also, 8 of 10 CSF samples from 8 patients who had three or more febrile convulsions and 1 of 7 CSF samples from patients who had a single febrile convulsion contained HHV-6 DNA. These data suggest that HHV-6 may invade the brain during the acute phase of exanthem subitum and that recurrence of febrile convulsions may be associated with reactivation of HHV-6.
Asunto(s)
Sistema Nervioso Central/microbiología , Exantema Súbito/complicaciones , Infecciones por Herpesviridae/complicaciones , Herpesvirus Humano 6/aislamiento & purificación , Convulsiones Febriles/complicaciones , Adolescente , Adulto , Secuencia de Bases , Niño , Preescolar , ADN Viral/líquido cefalorraquídeo , Exantema Súbito/líquido cefalorraquídeo , Exantema Súbito/microbiología , Femenino , Infecciones por Herpesviridae/líquido cefalorraquídeo , Infecciones por Herpesviridae/microbiología , Herpesvirus Humano 6/genética , Humanos , Masculino , Datos de Secuencia Molecular , Recurrencia , Convulsiones Febriles/líquido cefalorraquídeo , Convulsiones Febriles/microbiologíaRESUMEN
Escherichia coli osmosensor EnvZ is a protein histidine kinase that plays a central role in osmoregulation, a cellular adaptation process involving the His-Asp phosphorelay signal transduction system. Dimerization of the transmembrane protein is essential for its autophosphorylation and phosphorelay signal transduction functions. Here we present the NMR-derived structure of the homodimeric core domain (residues 223-289) of EnvZ that includes His 243, the site of autophosphorylation and phosphate transfer reactions. The structure comprises a four-helix bundle formed by two identical helix-turn-helix subunits, revealing the molecular assembly of two active sites within the dimeric kinase.
Asunto(s)
Proteínas de la Membrana Bacteriana Externa/química , Proteínas de Escherichia coli , Escherichia coli/enzimología , Complejos Multienzimáticos , Secuencia de Aminoácidos , Proteínas de la Membrana Bacteriana Externa/genética , Espectroscopía de Resonancia Magnética , Modelos Moleculares , Datos de Secuencia Molecular , Mutagénesis Sitio-Dirigida , Conformación Proteica , Homología de Secuencia de Aminoácido , SolucionesRESUMEN
Bacteria live in capricious environments, in which they must continuously sense external conditions in order to adjust their shape, motility and physiology. The histidine-aspartate phosphorelay signal-transduction system (also known as the two-component system) is important in cellular adaptation to environmental changes in both prokaryotes and lower eukaryotes. In this system, protein histidine kinases function as sensors and signal transducers. The Escherichia coli osmosensor, EnvZ, is a transmembrane protein with histidine kinase activity in its cytoplasmic region. The cytoplasmic region contains two functional domains: domain A (residues 223-289) contains the conserved histidine residue (H243), a site of autophosphorylation as well as transphosphorylation to the conserved D55 residue of response regulator OmpR, whereas domain B (residues 290-450) encloses several highly conserved regions (G1, G2, F and N boxes) and is able to phosphorylate H243. Here we present the solution structure of domain B, the catalytic core of EnvZ. This core has a novel protein kinase structure, distinct from the serine/threonine/tyrosine kinase fold, with unanticipated similarities to both heatshock protein 90 and DNA gyrase B.