RESUMEN
Sensor histidine kinase HprS, an oxidative stress sensor of Escherichia coli, senses reactive oxygen species (ROS) and reactive chlorine species (RCS), and is involved in the induction of oxidatively damaged protein repair periplasmic enzymes. We reinvestigated the roles of six methionine and four cysteine residues of HprS in the response to HClO, an RCS. The results of site-directed mutagenesis revealed that methionine residues in periplasmic and cytoplasmic regions (Met225) are involved in HprS activation. Interestingly, the Cys165Ser substitution reduced HprS activity, which was recovered by an additional Glu22Cys substitution. Our results demonstrate that the position of the inner membrane cysteine residues influences the extent of HprS activation in HClO sensing.
Asunto(s)
Cloro , Cisteína , Proteínas de Escherichia coli , Escherichia coli , Histidina Quinasa , Metionina , Cloro/metabolismo , Cisteína/metabolismo , Escherichia coli/metabolismo , Proteínas de Escherichia coli/metabolismo , Metionina/metabolismo , Proteínas/metabolismo , Racemetionina/metabolismo , Histidina Quinasa/metabolismoRESUMEN
Selective electrochemical production of valued chemicals is of significant importance but remains a great challenge in chemistry. Conventional approaches for enhancing reaction selectivity focus on the improvement of the catalysts themselves. In this work, we systematically studied the reaction kinetics and mass transport behavior of LaNiO3 nanocubes (LaNiO3 NCs) catalyzed hydrogen peroxide reduction reaction (HPRR) at ensemble and single nanoparticle levels using nano-impact electrochemistry (NIE). We find that the selectivity of HPRR was altered at individual random-walk nanoparticles as compared to their ensemble counterpart without changing the reaction kinetics, due to the significantly enhanced mass transport at single nanoparticles. This discovery offers the scope of new catalytic approaches for engineering electrochemical reactions in general.
RESUMEN
Surface plasmon resonance (SPR) spectroscopy is a rapidly developing technique for the study of ligand binding interactions with membrane proteins, which are the major molecular targets for validated drugs and for current and foreseeable drug discovery. SPR is label-free and capable of measuring real-time quantitative binding affinities and kinetics for membrane proteins interacting with ligand molecules using relatively small quantities of materials and has potential to be medium-throughput. The conventional SPR technique requires one binding component to be immobilised on a sensor chip whilst the other binding component in solution is flowed over the sensor surface; a binding interaction is detected using an optical method that measures small changes in refractive index at the sensor surface. This review first describes the basic SPR experiment and the challenges that have to be considered for performing SPR experiments that measure membrane protein-ligand binding interactions, most importantly having the membrane protein in a lipid or detergent environment that retains its native structure and activity. It then describes a wide-range of membrane protein systems for which ligand binding interactions have been characterised using SPR, including the major drug targets G protein-coupled receptors, and how challenges have been overcome for achieving this. Finally it describes some recent advances in SPR-based technology and future potential of the technique to screen ligand binding in the discovery of drugs. This article is part of a Special Issue entitled: Structural and biophysical characterisation of membrane protein-ligand binding.