Enterococci are gram-positive constituents of the normal human microflora, typically colonizing the intestinal tract and skin (34, 47). However, these organisms are capable of causing disease as opportunistic pathogens, mainly in immunocompromised patients (35, 58). The problem of enterococcal infection has been aggravated by the emergence in the past decade of multiple antibiotic resistance, w...

Two-component signal transduction (TCST) systems are the principal means for coordinating responses to environmental changes in bacteria as well as some plants, fungi, protozoa, and archaea. These systems typically consist of a receptor histidine kinase, which reacts to an extracellular signal by phosphorylating a cytoplasmic response regulator, causing a change in cellular behavior. Although s...

The two-component system, consisting of a histidine (His) protein kinase that senses a signal input and a response regulator that mediates the output, is an ancient and evolutionarily conserved signaling mechanism in prokaryotes and eukaryotes. The identification of 54 His protein kinases, His-containing phosphotransfer proteins, response regulators, and related proteins in Arabidopsis suggests...

In plants, two-component systems play important roles in signal transduction in response to environmental stimuli and growth regulators. Genetic and biochemical analyses indicate that sensory hybrid-type histidine kinases, ETR1 and its homologs, function as ethylene receptors and negative regulators in ethylene signaling. Two other hybrid-type histidine kinases, CKI1 and ATHK1, are implicated i...

Two-component signal transduction systems enable bacteria to sense, respond, and adapt to a wide range of environments, stressors, and growth conditions. In the prototypical two-component system, a sensor histidine kinase catalyzes its autophosphorylation and then subsequently transfers the phosphoryl group to a response regulator, which can then effect changes in cellular physiology, often by ...