9 research outputs found
Insights into anti-termination regulation of the hut operon in Bacillus subtilis: importance of the dual RNA-binding surfaces of HutP
The anti-termination protein, HutP, regulates the gene expression of the hut (histidine utilization) operon of Bacillus subtilis, by destabilizing the hut terminator RNA located upstream of the coding region encoding l-histidine degradation enzymes. On the basis of biochemical, in vivo and X-ray structural analyses, we now report that HutP uses its dual RNA-binding surfaces to access two XAG-rich regions (sites I and II) within the terminator RNA to mediate the destabilization process. In this process, HutP initiates destabilization at the 5′-end of its mRNA by binding to the first XAG-rich region (site I) and then accesses the second XAG-rich region (site II), located downstream of the stable G-C-rich segment of the terminator stem. By this action, HutP appears to disrupt the G-C-rich terminator stem, and thus prevents premature termination of transcription in the RNA segment preceding the regions encoding for the histidine degradation enzymes
The Role of Microscopic Interactions for Effective Antibiotic Delivery across the Bacterial Outer Membrane
A Structural Study of Ion Permeation in OmpF Porin from Anomalous X‑ray Diffraction and Molecular Dynamics Simulations
OmpF, a multiionic porin from <i>Escherichia coli</i>, is a useful protypical model system for
addressing general questions
about electrostatic interactions in the confinement of an aqueous
molecular pore. Here, favorable anion locations in the OmpF pore were
mapped by anomalous X-ray scattering of Br<sup>–</sup> ions
from four different crystal structures and compared with Mg<sup>2+</sup> sites and Rb<sup>+</sup> sites from a previous anomalous diffraction
study to provide a complete picture of cation and anion transfer paths
along the OmpF channel. By comparing structures with various crystallization
conditions, we find that anions bind in discrete clusters along the
entire length of the OmpF pore, whereas cations find conserved binding
sites with the extracellular, surface-exposed loops. Results from
molecular dynamics simulations are consistent with the experimental
data and help highlight the critical residues that preferentially
contact either cations or anions during permeation. Analysis of these
results provides new insights into the molecular mechanisms that determine
ion selectivity in OmpF porin
A Structural Study of Ion Permeation in OmpF Porin from Anomalous X‑ray Diffraction and Molecular Dynamics Simulations
OmpF, a multiionic porin from <i>Escherichia coli</i>, is a useful protypical model system for
addressing general questions
about electrostatic interactions in the confinement of an aqueous
molecular pore. Here, favorable anion locations in the OmpF pore were
mapped by anomalous X-ray scattering of Br<sup>–</sup> ions
from four different crystal structures and compared with Mg<sup>2+</sup> sites and Rb<sup>+</sup> sites from a previous anomalous diffraction
study to provide a complete picture of cation and anion transfer paths
along the OmpF channel. By comparing structures with various crystallization
conditions, we find that anions bind in discrete clusters along the
entire length of the OmpF pore, whereas cations find conserved binding
sites with the extracellular, surface-exposed loops. Results from
molecular dynamics simulations are consistent with the experimental
data and help highlight the critical residues that preferentially
contact either cations or anions during permeation. Analysis of these
results provides new insights into the molecular mechanisms that determine
ion selectivity in OmpF porin
A Structural Study of Ion Permeation in OmpF Porin from Anomalous X‑ray Diffraction and Molecular Dynamics Simulations
OmpF, a multiionic porin from <i>Escherichia coli</i>, is a useful protypical model system for
addressing general questions
about electrostatic interactions in the confinement of an aqueous
molecular pore. Here, favorable anion locations in the OmpF pore were
mapped by anomalous X-ray scattering of Br<sup>–</sup> ions
from four different crystal structures and compared with Mg<sup>2+</sup> sites and Rb<sup>+</sup> sites from a previous anomalous diffraction
study to provide a complete picture of cation and anion transfer paths
along the OmpF channel. By comparing structures with various crystallization
conditions, we find that anions bind in discrete clusters along the
entire length of the OmpF pore, whereas cations find conserved binding
sites with the extracellular, surface-exposed loops. Results from
molecular dynamics simulations are consistent with the experimental
data and help highlight the critical residues that preferentially
contact either cations or anions during permeation. Analysis of these
results provides new insights into the molecular mechanisms that determine
ion selectivity in OmpF porin
A Structural Study of Ion Permeation in OmpF Porin from Anomalous X‑ray Diffraction and Molecular Dynamics Simulations
OmpF, a multiionic porin from <i>Escherichia coli</i>, is a useful protypical model system for
addressing general questions
about electrostatic interactions in the confinement of an aqueous
molecular pore. Here, favorable anion locations in the OmpF pore were
mapped by anomalous X-ray scattering of Br<sup>–</sup> ions
from four different crystal structures and compared with Mg<sup>2+</sup> sites and Rb<sup>+</sup> sites from a previous anomalous diffraction
study to provide a complete picture of cation and anion transfer paths
along the OmpF channel. By comparing structures with various crystallization
conditions, we find that anions bind in discrete clusters along the
entire length of the OmpF pore, whereas cations find conserved binding
sites with the extracellular, surface-exposed loops. Results from
molecular dynamics simulations are consistent with the experimental
data and help highlight the critical residues that preferentially
contact either cations or anions during permeation. Analysis of these
results provides new insights into the molecular mechanisms that determine
ion selectivity in OmpF porin