7 research outputs found
DataSheet1_Probing the conformational changes of in vivo overexpressed cell cycle regulator 6S ncRNA.pdf
The non-coding 6S RNA is a master regulator of the cell cycle in bacteria which binds to the RNA polymerase-σ70 holoenzyme during the stationary phase to inhibit transcription from the primary σ factor. Inhibition is reversed upon outgrowth from the stationary phase by synthesis of small product RNA transcripts (pRNAs). 6S and its complex with a pRNA were structurally characterized using Small Angle X-ray Scattering. The 3D models of 6S and 6S:pRNA complex presented here, demonstrate that the fairly linear and extended structure of 6S undergoes a major conformational change upon binding to pRNA. In particular, 6S:pRNA complex formation is associated with a compaction of the overall 6S size and an expansion of its central domain. Our structural models are consistent with the hypothesis that the resultant particle has a shape and size incompatible with binding to RNA polymerase-σ70. Overall, by use of an optimized in vivo methodological approach, especially useful for structural studies, our study considerably improves our understanding of the structural basis of 6S regulation by offering a mechanistic glimpse of the 6S transcriptional control.</p
Image4_Probing the conformational changes of in vivo overexpressed cell cycle regulator 6S ncRNA.TIF
The non-coding 6S RNA is a master regulator of the cell cycle in bacteria which binds to the RNA polymerase-σ70 holoenzyme during the stationary phase to inhibit transcription from the primary σ factor. Inhibition is reversed upon outgrowth from the stationary phase by synthesis of small product RNA transcripts (pRNAs). 6S and its complex with a pRNA were structurally characterized using Small Angle X-ray Scattering. The 3D models of 6S and 6S:pRNA complex presented here, demonstrate that the fairly linear and extended structure of 6S undergoes a major conformational change upon binding to pRNA. In particular, 6S:pRNA complex formation is associated with a compaction of the overall 6S size and an expansion of its central domain. Our structural models are consistent with the hypothesis that the resultant particle has a shape and size incompatible with binding to RNA polymerase-σ70. Overall, by use of an optimized in vivo methodological approach, especially useful for structural studies, our study considerably improves our understanding of the structural basis of 6S regulation by offering a mechanistic glimpse of the 6S transcriptional control.</p
Image2_Probing the conformational changes of in vivo overexpressed cell cycle regulator 6S ncRNA.TIF
The non-coding 6S RNA is a master regulator of the cell cycle in bacteria which binds to the RNA polymerase-σ70 holoenzyme during the stationary phase to inhibit transcription from the primary σ factor. Inhibition is reversed upon outgrowth from the stationary phase by synthesis of small product RNA transcripts (pRNAs). 6S and its complex with a pRNA were structurally characterized using Small Angle X-ray Scattering. The 3D models of 6S and 6S:pRNA complex presented here, demonstrate that the fairly linear and extended structure of 6S undergoes a major conformational change upon binding to pRNA. In particular, 6S:pRNA complex formation is associated with a compaction of the overall 6S size and an expansion of its central domain. Our structural models are consistent with the hypothesis that the resultant particle has a shape and size incompatible with binding to RNA polymerase-σ70. Overall, by use of an optimized in vivo methodological approach, especially useful for structural studies, our study considerably improves our understanding of the structural basis of 6S regulation by offering a mechanistic glimpse of the 6S transcriptional control.</p
Image1_Probing the conformational changes of in vivo overexpressed cell cycle regulator 6S ncRNA.TIF
The non-coding 6S RNA is a master regulator of the cell cycle in bacteria which binds to the RNA polymerase-σ70 holoenzyme during the stationary phase to inhibit transcription from the primary σ factor. Inhibition is reversed upon outgrowth from the stationary phase by synthesis of small product RNA transcripts (pRNAs). 6S and its complex with a pRNA were structurally characterized using Small Angle X-ray Scattering. The 3D models of 6S and 6S:pRNA complex presented here, demonstrate that the fairly linear and extended structure of 6S undergoes a major conformational change upon binding to pRNA. In particular, 6S:pRNA complex formation is associated with a compaction of the overall 6S size and an expansion of its central domain. Our structural models are consistent with the hypothesis that the resultant particle has a shape and size incompatible with binding to RNA polymerase-σ70. Overall, by use of an optimized in vivo methodological approach, especially useful for structural studies, our study considerably improves our understanding of the structural basis of 6S regulation by offering a mechanistic glimpse of the 6S transcriptional control.</p
Image3_Probing the conformational changes of in vivo overexpressed cell cycle regulator 6S ncRNA.TIF
The non-coding 6S RNA is a master regulator of the cell cycle in bacteria which binds to the RNA polymerase-σ70 holoenzyme during the stationary phase to inhibit transcription from the primary σ factor. Inhibition is reversed upon outgrowth from the stationary phase by synthesis of small product RNA transcripts (pRNAs). 6S and its complex with a pRNA were structurally characterized using Small Angle X-ray Scattering. The 3D models of 6S and 6S:pRNA complex presented here, demonstrate that the fairly linear and extended structure of 6S undergoes a major conformational change upon binding to pRNA. In particular, 6S:pRNA complex formation is associated with a compaction of the overall 6S size and an expansion of its central domain. Our structural models are consistent with the hypothesis that the resultant particle has a shape and size incompatible with binding to RNA polymerase-σ70. Overall, by use of an optimized in vivo methodological approach, especially useful for structural studies, our study considerably improves our understanding of the structural basis of 6S regulation by offering a mechanistic glimpse of the 6S transcriptional control.</p
Hydrophobic Molecules Infiltrating into the Poly(ethylene glycol) Domain of the Core/Shell Interface of a Polymeric Micelle: Evidence Obtained with Anomalous Small-Angle X‑ray Scattering
Polymeric micelles have been extensively studied as nanoscale
drug
carriers. Knowing the inner structure of polymeric micelles that encapsulate
hydrophobic drugs is important to design effective carriers. In our
study, the hydrophobic compound tetrabromocathecol (TBC) was chosen
as a drug-equivalent model molecule. The bromine atoms in TBC act
as probes in anomalous small-angle X-ray scattering (ASAXS) allowing
for its localization in the polymeric micelles whose shape and size
were determined by normal small-angle X-ray scattering (SAXS). Light
scattering measurements coupled with field flow fractionation were
also carried out to determine the aggregation number of micelles.
A core–corona spherical model was used to explain the shape
of the micelles, while the distribution of bromine atoms was explained
with a hard-sphere model. Interestingly, the radius of the spherical
region populated with bromine atoms was larger than the one of the
sphere corresponding to the hydrophobic core of the micelle. This
result suggests that the TBC molecules infiltrate the PEG hydrophilic
domain in the vicinity of the core/shell interface. The results of
light scattering and SAXS indicate that the PEG chains at the shell
region are densely packed, and thus the PEG domain close to the interface
has enough hydrophobicity to tolerate the presence of hydrophobic
compounds
X‑ray Scattering from Immunostimulatory Tetrapod-Shaped DNA in Aqueous Solution To Explore Its Biological Activity–Conformation Relationship
We carried out synchrotron X-ray
scattering experiments from four
DNA supermolecules designed to form tetrapod shapes; these supermolecules
had different sequences but identical numbers of total base pairs,
and each contained an immunostimulatory CpG motif. We confirmed that
the supermolecules did indeed form the expected tetrapod shape. The
sample that had the largest radius of gyration (<i>R</i><sub>g</sub>) induced the most cytokine secretion from cultured immune
cells. Structural analysis in combination with a rigid tetrapod model
and an atomic scale DNA model revealed that the larger <i>R</i><sub>g</sub> can be ascribed to dissociation of the DNA double strands
in the central connecting portion of the DNA tetrapod. This finding
suggests that the biological activity is related to the ease with
which single DNA strands can be formed