scholarly journals Actinoplanes missouriensiss is a rare actinomycete that forms terminal sporangia containing a few hundred flagellated, motile spores (shown here in a scanning EM image). The TcrA response regulator controls sporangium formation and flagellar biogenesis th

2018 ◽  
Vol 107 (6) ◽  
pp. i-i
Keyword(s):  
Response Regulator ◽  
Scanning Em ◽  
Flagellar Biogenesis

scholarly journals Helicobacter pylori FlhA Binds the Sensor Kinase and Flagellar Gene Regulatory Protein FlgS with High Affinity

2015 ◽  
Vol 197 (11) ◽  
pp. 1886-1892 ◽  
Author(s):  
Jennifer Tsang ◽  
Takanori Hirano ◽  
Timothy R. Hoover ◽  
Jonathan L. McMurry
Keyword(s):  
Helicobacter Pylori ◽  
Response Regulator ◽  
Regulatory Protein ◽  
Kinase Domain ◽  
Optical Biosensing ◽  
Content Type ◽  
High Affinity ◽  
Flagellar Assembly ◽  
Flagellar Biogenesis

ABSTRACTFlagellar biogenesis is a complex process that involves multiple checkpoints to coordinate transcription of flagellar genes with the assembly of the flagellum. InHelicobacter pylori, transcription of the genes needed in the middle stage of flagellar biogenesis is governed by RpoN and the two-component system consisting of the histidine kinase FlgS and response regulator FlgR. In response to an unknown signal, FlgS autophosphorylates and transfers the phosphate to FlgR, initiating transcription from RpoN-dependent promoters. In the present study, export apparatus protein FlhA was examined as a potential signal protein. Deletion of its N-terminal cytoplasmic sequence dramatically decreased expression of two RpoN-dependent genes,flaBandflgE. Optical biosensing demonstrated a high-affinity interaction between FlgS and a peptide consisting of residues 1 to 25 of FlhA (FlhANT). TheKD(equilibrium dissociation constant) was 21 nM and was characterized by fast-on (kon= 2.9 × 104M−1s−1) and slow-off (koff= 6.2 × 10−4s−1) kinetics. FlgS did not bind peptides consisting of smaller fragments of the FlhANTsequence. Analysis of binding to purified fragments of FlgS demonstrated that the C-terminal portion of the protein containing the kinase domain binds FlhANT. FlhANTbinding did not stimulate FlgS autophosphorylationin vitro, suggesting that FlhA facilitates interactions between FlgS and other structures required to stimulate autophosphorylation.IMPORTANCEThe high-affinity binding of FlgS to FlhA characterized in this study points to an additional role for FlhA in flagellar assembly. Beyond its necessity for type III secretion, the N-terminal cytoplasmic sequence of FlhA is required for RpoN-dependent gene expression via interaction with the C-terminal kinase domain of FlgS.

The ultrastructure of the double membrane-bound bodies and endoplasmic reticulum in serial sections of wheat spot mosaic-affected wheat plants

1990 ◽  
Vol 48 (3) ◽  
pp. 694-695
Author(s):  
M. H. Chen ◽  
C. Hiruki
Keyword(s):  
Endoplasmic Reticulum ◽  
High Resolution ◽  
Membrane Structure ◽  
Mosaic Disease ◽  
Serial Sections ◽  
Thin Sections ◽  
Double Membrane ◽  
Southern Alberta ◽  
Membrane Bound ◽  
Scanning Em

Wheat spot mosaic disease was first discovered in southern Alberta, Canada, in 1956. A hitherto unidentified disease-causing agent, transmitted by the eriophyid mite, caused chlorosis, stunting and finally severe necrosis resulting in the death of the affected plants. Double membrane-bound bodies (DMBB), 0.1-0.2 μm in diameter were found to be associated with the disease.Young tissues of leaf and root from 4-wk-old infected wheat plants were fixed, dehydrated, and embedded in Spurr’s resin. Serial sections were collected on slot copper grids and stained. The thin sections were then examined with a Hitachi H-7000 TEM at 75 kV. The membrane structure of the DMBBs was studied by numbering them individually and tracing along the sections to see any physical connection with endoplasmic reticulum (ER) membranes. For high resolution scanning EM, a modification of Tanaka’s method was used. The specimens were examined with a Hitachi Model S-570 SEM in its high resolution mode at 20 kV.

scholarly journals Signal Transduction and Regulatory Mechanisms Involved in Control of the σS (RpoS) Subunit of RNA Polymerase

2002 ◽  
Vol 66 (3) ◽  
pp. 373-395 ◽  
Author(s):  
Regine Hengge-Aronis
Keyword(s):  
Rna Polymerase ◽  
Translational Control ◽  
Current Knowledge ◽  
Response Regulator ◽  
Regulatory System ◽  
Stress Conditions ◽  
Acidic Ph ◽  
High Osmolarity ◽  
Multiple Signal ◽  
Rpos Mrna

SUMMARY The σS (RpoS) subunit of RNA polymerase is the master regulator of the general stress response in Escherichia coli and related bacteria. While rapidly growing cells contain very little σS, exposure to many different stress conditions results in rapid and strong σS induction. Consequently, transcription of numerous σS-dependent genes is activated, many of which encode gene products with stress-protective functions. Multiple signal integration in the control of the cellular σS level is achieved by rpoS transcriptional and translational control as well as by regulated σS proteolysis, with various stress conditions differentially affecting these levels of σS control. Thus, a reduced growth rate results in increased rpoS transcription whereas high osmolarity, low temperature, acidic pH, and some late-log-phase signals stimulate the translation of already present rpoS mRNA. In addition, carbon starvation, high osmolarity, acidic pH, and high temperature result in stabilization of σS, which, under nonstress conditions, is degraded with a half-life of one to several minutes. Important cis-regulatory determinants as well as trans-acting regulatory factors involved at all levels of σS regulation have been identified. rpoS translation is controlled by several proteins (Hfq and HU) and small regulatory RNAs that probably affect the secondary structure of rpoS mRNA. For σS proteolysis, the response regulator RssB is essential. RssB is a specific direct σS recognition factor, whose affinity for σS is modulated by phosphorylation of its receiver domain. RssB delivers σS to the ClpXP protease, where σS is unfolded and completely degraded. This review summarizes our current knowledge about the molecular functions and interactions of these components and tries to establish a framework for further research on the mode of multiple signal input into this complex regulatory system.

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