scholarly journals Role of RcsF in Signaling to the Rcs Phosphorelay Pathway in Escherichia coli

2005 ◽  
Vol 187 (19) ◽  
pp. 6770-6778 ◽  
Author(s):  
Nadim Majdalani ◽  
Michael Heck ◽  
Valerie Stout ◽  
Susan Gottesman
Keyword(s):  
Escherichia Coli ◽  
Cell Surface ◽  
Small Rna ◽  
Kinase Activity ◽  
Response Regulator ◽  
Constitutive Expression ◽  
Activation Mechanism ◽  
Sensor Kinase ◽  
High Level

ABSTRACT The rcs phosphorelay pathway components were originally identified as regulators of capsule synthesis. In addition to the transmembrane sensor kinase RcsC, the RcsA coregulator, and the response regulator RcsB, two new components have been characterized, RcsD and RcsF. RcsD, the product of the yojN gene, now renamed rcsD, acts as a phosphorelay between RcsC and RcsB. Transcription of genes for capsule synthesis (cps) requires both RcsA and RcsB; transcription of other promoters, including that for the small RNA RprA, requires only RcsB. RcsF was described as an alternative sensor kinase for RcsB. We have examined the role of RcsF in the activation of both the rprA and cps promoters. We find that a number of signals that lead to activation of the phosphorelay require both RcsF and RcsC; epistasis experiments place RcsF upstream of RcsC. The RcsF sequence is characteristic of lipoproteins, consistent with a role in sensing cell surface perturbation and transmitting this signal to RcsC. Activation of RcsF does not require increased transcription of the gene, suggesting that modification of the RcsF protein may act as an activating signal. Signals from RcsC require RcsD to activate RcsB. Sequencing of an rcsC allele, rcsC137, that leads to high-level constitutive expression of both cps and rprA suggests that the response regulator domain of RcsC plays a role in negatively regulating the kinase activity of RcsC. The phosphorelay and the variation in the activation mechanism (dependent upon or independent of RcsA) provide multiple steps for modulating the output from this system.

scholarly journals The Extension of the Fourth Transmembrane Helix of the Sensor Kinase KdpD of Escherichia coli Is Involved in Sensing

2007 ◽  
Vol 189 (20) ◽  
pp. 7326-7334 ◽  
Author(s):  
Petra Zimmann ◽  
Anne Steinbrügge ◽  
Maren Schniederberend ◽  
Kirsten Jung ◽  
Karlheinz Altendorf
Keyword(s):  
Escherichia Coli ◽  
Response Regulator ◽  
Transmembrane Helix ◽  
Random Mutagenesis ◽  
Constitutive Expression ◽  
Single Amino Acid ◽  
Sensor Kinase ◽  
Fold Induction ◽  
Autokinase Activity

ABSTRACT The KdpD sensor kinase and the KdpE response regulator control expression of the kdpFABC operon coding for the KdpFABC high-affinity K+ transport system of Escherichia coli. In search of a distinct part of the input domain of KdpD which is solely responsible for K+ sensing, sequences of kdpD encoding the transmembrane region and adjacent N-terminal and C-terminal extensions were subjected to random mutagenesis. Nine KdpD derivatives were identified that had lost tight regulation of kdpFABC expression. They all carried single amino acid replacements located in a region encompassing the fourth transmembrane helix and the adjacent arginine cluster of KdpD. All mutants exhibited high levels of kdpFABC expression regardless of the external K+ concentration. However, 3- to 14-fold induction was observed under extreme K+-limiting conditions and in response to an osmotic upshift when sucrose was used as an osmolyte. These KdpD derivatives were characterized by a reduced phosphatase activity in comparison to the autokinase activity in vitro, which explains constitutive expression. Whereas for wild-type KdpD the autokinase activity and also, in turn, the phosphotransfer activity to KdpE were inhibited by increasing concentrations of K+, both activities were unaffected in the KdpD derivatives. These data clearly show that the extension of the fourth transmembrane helix encompassing the arginine cluster is mainly involved in sensing both K+ limitation and osmotic upshift, which may not be separated mechanistically.

scholarly journals The KdpD Sensor Kinase of Escherichia coli Responds to Several Distinct Signals To Turn on Expression of the Kdp Transport System

2015 ◽  
Vol 198 (2) ◽  
pp. 212-220 ◽  
Author(s):  
Wolfgang Epstein
Keyword(s):  
Escherichia Coli ◽  
Growth Rate ◽  
Transport System ◽  
Kinase Activity ◽  
Response Regulator ◽  
Sensor Kinase ◽  
Monovalent Cations ◽  
Two Component System ◽  
Content Type ◽  
E Coli

ABSTRACTKdp, one of three saturable K+uptake systems inEscherichia coli, is the system with the highest affinity for K+and the only one whose expression is strongly controlled by medium K+concentration. Expression is controlled by a two-component system of KdpD, the sensor kinase, and KdpE, the response regulator. There is general agreement that expression occurs when the growth rate of cells begins to become limited by K+availability. How K+limitation results in expression has been controversial. Studying the roles of the major components of the growth medium shows that KdpD senses at least two distinct signals inside the cell, those of Na+and NH4+, and it probably senses other monovalent cations in the cell. KdpD does not sense turgor.IMPORTANCEThe expression of the Kdp K+transport system ofE. colioccurs when cells become limited in their growth rate by the availability of K+. Cells sense limited K+and try to compensate by taking up other monovalent cations, particularly Na+and NH4+. These cations are sensed in the cytoplasm by the KdpD response regulator, presumably to stimulate its kinase activity. It is shown that KdpD does not sense turgor, as was suggested earlier.

scholarly journals Mechanisms of Dinucleotide Repeat Instability in Escherichia coli

Genetics ◽  
2000 ◽  
Vol 154 (2) ◽  
pp. 533-542
Author(s):  
Marc Bichara ◽  
Isabelle Pinet ◽  
Sylvie Schumacher ◽  
Robert P P Fuchs
Keyword(s):  
Escherichia Coli ◽  
Mismatch Repair ◽  
Genetic Instability ◽  
Positional Cloning ◽  
Dinucleotide Repeats ◽  
Disease Pathogenesis ◽  
Complementary Sequence ◽  
Phylogenetic Studies ◽  
High Level

Abstract The high level of polymorphism of microsatellites has been used for a variety of purposes such as positional cloning of genes associated with diseases, forensic medicine, and phylogenetic studies. The discovery that microsatellites are associated with human diseases, not only as markers of risk but also directly in disease pathogenesis, has triggered a renewed interest in understanding the mechanism of their instability. In this work we have investigated the role of DNA replication, long patch mismatch repair, and transcription on the genetic instability of all possible combinations of dinucleotide repeats in Escherichia coli. We show that the (GpC) and (ApT) self-complementary sequence repeats are the most unstable and that the mode of replication plays an important role in their instability. We also found that long patch mismatch repair is involved in avoiding both short deletion and expansion events and also in instabilities resulting from the processing of bulges of 6 to 8 bp for the (GpT/ApC)- and (ApG/CpT)-containing repeats. For each dinucleotide sequence repeat, we propose models for instability that involve the possible participation of unusual secondary structures.

scholarly journals Molecular survey of mcr1 and mcr2 plasmid mediated colistin resistance genes in Escherichia coli isolates of animal origin in Iran

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Kayhan Ilbeigi ◽  
Mahdi Askari Badouei ◽  
Hossein Vaezi ◽  
Hassan Zaheri ◽  
Sina Aghasharif ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Resistance Genes ◽  
Companion Animals ◽  
Multidrug Resistant ◽  
Animal Origin ◽  
Colistin Resistance ◽  
E Coli ◽  
High Level ◽  
Farming Industry

Abstract Objectives The emergence of colistin-resistant Enterobacteriaceae from human and animal sources is one of the major public health concerns as colistin is the last-resort antibiotic for treating infections caused by multidrug-resistant Gram-negative bacteria. We aimed to determine the prevalence of the prototype widespread colistin resistance genes (mcr-1 and mcr-2) among commensal and pathogenic Escherichia coli strains isolated from food-producing and companion animals in Iran. Results A total of 607 E. coli isolates which were previously collected from different animal sources between 2008 and 2016 used to uncover the possible presence of plasmid-mediated colistin resistance genes (mcr-1 and mcr-2) by PCR. Overall, our results could not confirm the presence of any mcr-1 or mcr-2 positive E. coli among the studied isolates. It is concluded that despite the important role of food-producing animals in transferring the antibiotic resistance, they were not the main source for carriage of mcr-1 and mcr-2 in Iran until 2016. This study suggests that the other mcr variants (mcr-3 to mcr-9) might be responsible for conferring colistin resistance in animal isolates in Iran. The possible linkage between pig farming industry and high level of mcr carriage in some countries needs to be clarified in future prospective studies.

Role of nitric oxide in the control of renin secretion

1998 ◽  
Vol 275 (6) ◽  
pp. F849-F862 ◽  
Author(s):  
Armin Kurtz ◽  
Charlotte Wagner
Keyword(s):  
Nitric Oxide ◽  
Kinase Activity ◽  
Constitutive Expression ◽  
Juxtaglomerular Apparatus ◽  
Renin Secretion ◽  
Protein Kinase Activity ◽  
Dependent Protein Kinase ◽  
Dependent Protein ◽  
Permissive Role

Because of the significant constitutive expression of NO synthases in the juxtaglomerular apparatus, nitric oxide (NO) is considered as a likely modulator of renin secretion. In most instances, NO appears as a tonic enhancer of renin secretion, acting via inhibition of cAMP degradation through the action of cGMP. Depending on as yet unknown factors, the stimulatory effect of NO on renin secretion may also switch to an inhibitory one that is compatible with the inhibition of renin secretion by cGMP-dependent protein kinase activity. Whether NO plays a direct regulatory role or a more permissive role in the control of renin secretion remains to be answered.

scholarly journals Investigation of the Role of Electrostatic Charge in Activation of the Escherichia coli Response Regulator CheY

2003 ◽  
Vol 185 (21) ◽  
pp. 6385-6391 ◽  
Author(s):  
Jenny G. Smith ◽  
Jamie A. Latiolais ◽  
Gerald P. Guanga ◽  
Sindhura Citineni ◽  
Ruth E. Silversmith ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Signal Transduction ◽  
Amino Acid ◽  
Active Site ◽  
Response Regulator ◽  
Residual Activity ◽  
Phosphoryl Group ◽  
Sensor Kinase ◽  
Amino Acid Substitutions ◽  
Flagellar Rotation

ABSTRACT In a two-component regulatory system, an important means of signal transduction in microorganisms, a sensor kinase phosphorylates a response regulator protein on an aspartyl residue, resulting in activation. The active site of the response regulator is highly charged (containing a lysine, the phosphorylatable aspartate, two additional aspartates involved in metal binding, and an Mg2+ ion), and introduction of the dianionic phosphoryl group results in the repositioning of charged moieties. Furthermore, substitution of one of the Mg2+-coordinating aspartates with lysine or arginine in the Escherichia coli chemotaxis response regulator CheY results in phosphorylation-independent activation. In order to examine the consequences of altered charge distribution for response regulator activity and to identify possible additional amino acid substitutions that result in phosphorylation-independent activation, we made 61 CheY mutants in which residues close to the site of phosphorylation (Asp57) were replaced by various charged amino acids. Most substitutions (47 of 61) resulted in the complete loss of CheY activity, as measured by the inability to support clockwise flagellar rotation. However, 10 substitutions, all introducing a new positive charge, resulted in the loss of chemotaxis but in the retention of some clockwise flagellar rotation. Of the mutants in this set, only the previously identified CheY13DK and CheY13DR mutants displayed clockwise activity in the absence of the CheA sensor kinase. The absence of negatively charged substitution mutants with residual activity suggests that the introduction of additional negative charges into the active site is particularly deleterious for CheY function. Finally, the spatial distribution of positions at which amino acid substitutions are functionally tolerated or not tolerated is consistent with the presently accepted mechanism of response regulator activation and further suggests a possible role for Met17 in signal transduction by CheY.

Evidence against the physiological role of acetyl phosphate in the phosphorylation of the ArcA response regulator in Escherichia coli

2009 ◽  
Vol 47 (5) ◽  
pp. 657-662 ◽  
Author(s):  
Xueqiao Liu ◽  
Gabriela R. Peña Sandoval ◽  
Barry L. Wanner ◽  
Won Seok Jung ◽  
Dimitris Georgellis ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Response Regulator ◽  
Physiological Role ◽  
Acetyl Phosphate

scholarly journals Longitudinal Study of Escherichia coli O157:H7 in a Beef Cattle Feedlot and Role of High-Level Shedders in Hide Contamination

2009 ◽  
Vol 75 (20) ◽  
pp. 6515-6523 ◽  
Author(s):  
Terrance M. Arthur ◽  
James E. Keen ◽  
Joseph M. Bosilevac ◽  
Dayna M. Brichta-Harhay ◽  
Norasak Kalchayanand ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Longitudinal Study ◽  
Beef Cattle ◽  
Intervention Studies ◽  
High Density ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
High Level ◽  
Cattle Feedlot

ABSTRACT The objectives of the study described here were (i) to investigate the dynamics of Escherichia coli O157:H7 fecal and hide prevalence over a 9-month period in a feedlot setting and (ii) to determine how animals shedding E. coli O157:H7 at high levels affect the prevalence and levels of E. coli O157:H7 on the hides of other animals in the same pen. Cattle (n = 319) were distributed in 10 adjacent pens, and fecal and hide levels of E. coli O157:H7 were monitored. When the fecal pen prevalence exceeded 20%, the hide pen prevalence was usually (25 of 27 pens) greater than 80%. Sixteen of 19 (84.2%) supershedder (>104 CFU/g) pens had a fecal prevalence greater than 20%. Significant associations with hide and high-level hide (≥40 CFU/100 cm2) contamination were identified for (i) a fecal prevalence greater than 20%, (ii) the presence of one or more high-density shedders (≥200 CFU/g) in a pen, and (iii) the presence of one or more supershedders in a pen. The results presented here suggest that the E. coli O157:H7 fecal prevalence should be reduced below 20% and the levels of shedding should be kept below 200 CFU/g to minimize the contamination of cattle hides. Also, large and unpredictable fluctuations within and between pens in both fecal and hide prevalence of E. coli O157:H7 were detected and should be used as a guide when preharvest studies, particularly preharvest intervention studies, are designed.

scholarly journals Survival of uropathogenic Escherichia coli in the murine urinary tract is dependent on OmpR

Microbiology ◽  
2009 ◽  
Vol 155 (6) ◽  
pp. 1832-1839 ◽  
Author(s):  
William R. Schwan
Keyword(s):  
Escherichia Coli ◽  
Urinary Tract ◽  
Wild Type Strain ◽  
Response Regulator ◽  
Phosphorylation Site ◽  
Regulatory System ◽  
Growth Defect ◽  
Wild Type ◽  
Log Reduction

Uropathogenic Escherichia coli (UPEC) can grow in environments with significantly elevated osmolarities, such as murine and human urinary tracts. OmpR is the response regulator part of a two-component OmpR–EnvZ regulatory system that responds to osmotic stresses. To determine the role of OmpR in UPEC survival, a ΔompR mutant was created in the UPEC clinical isolate NU149. The ΔompR mutant had a growth defect compared with the wild-type strain under osmotic stress conditions; this defect was complemented by the full-length ompR gene on a plasmid, but not with a mutant OmpR with an alanine substitution for aspartic acid at the phosphorylation site at position 55. Furthermore, the ΔompR mutant displayed up to 2-log reduction in bacterial cell numbers in murine bladders and kidneys compared with wild-type bacteria after 5 days of infection. The ability of the bacteria to survive was restored to wild-type levels when the ΔompR mutant strain was complemented with wild-type ompR, but not when the alanine-substituted ompR gene was used. This study has fulfilled molecular Koch's postulates by showing the pivotal role OmpR plays in UPEC survival within the murine urinary tract.

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