Uridylylation of the PII protein from Herbaspirillum seropedicae

2001 ◽  
Vol 47 (4) ◽  
pp. 309-314 ◽  
Author(s):  
Elaine M Benelli ◽  
Martin Buck ◽  
Emanuel Maltempi de Souza ◽  
Marshall Geoffrey Yates ◽  
Fabio O Pedrosa
Keyword(s):  
Escherichia Coli ◽  
Signal Transduction ◽  
Nitrogen Level ◽  
Signal Transducer ◽  
Cell Free Extract ◽  
Herbaspirillum Seropedicae ◽  
Pii Protein ◽  
A Cell ◽  
Probable Role

The PII protein is apparently involved in the control of NifA activity in Herbaspirillum seropedicae. To evaluate the probable role of PII in signal transduction, uridylylation assays were conducted with purified H. seropedicae PII and Escherichia coli GlnD, or a cell-free extract of H. seropedicae as sources of uridylylating activity. The results showed that α-ketoglutarate and ATP stimulate uridylylation whereas glutamine inhibits uridylylation. Deuridylylation of PII-UMP was dependent on glutamine and inhibited by ATP and α-ketoglutarate. PII uridylylation and (or) deuridylylation in response to these effectors suggests that PII is a nitrogen level signal transducer in H. seropedicae.Key words: nitrogen regulation, uridylylation, PII protein, Herbaspirillum seropedicae.

scholarly journals Role of Escherichia coli Nitrogen Regulatory Genes in the Nitrogen Response of the Azotobacter vinelandiiNifL-NifA Complex

2001 ◽  
Vol 183 (10) ◽  
pp. 3076-3082 ◽  
Author(s):  
Francisca Reyes-Ramirez ◽  
Richard Little ◽  
Ray Dixon
Keyword(s):  
Escherichia Coli ◽  
Signal Transduction ◽  
Nitrogen Control ◽  
Fixed Nitrogen ◽  
Nitrogen Response ◽  
E Coli ◽  
Nitrogen Excess

ABSTRACT The redox-sensing flavoprotein NifL inhibits the activity of the nitrogen fixation (nif)-specific transcriptional activator NifA in Azotobacter vinelandii in response to molecular oxygen and fixed nitrogen. Although the mechanism whereby the A. vinelandii NifL-NifA system responds to fixed nitrogen in vivo is unknown, the glnK gene, which encodes a PII-like signal transduction protein, has been implicated in nitrogen control. However, the precise function of A. vinelandii glnK in this response is difficult to establish because of the essential nature of this gene. We have shown previously that A. vinelandii NifL is able to respond to fixed nitrogen to control NifA activity when expressed inEscherichia coli. In this study, we investigated the role of the E. coli PII-like signal transduction proteins in nitrogen control of the A. vinelandii NifL-NifA regulatory system in vivo. In contrast to recent findings with Klebsiella pneumoniae NifL, our results indicate that neither the E. coli PII nor GlnK protein is required to relieve inhibition byA. vinelandii NifL under nitrogen-limiting conditions. Moreover, disruption of both the E. coli glnB andntrC genes resulted in a complete loss of nitrogen regulation of NifA activity by NifL. We observe that glnB ntrC and glnB glnK ntrC mutant strains accumulate high levels of intracellular 2-oxoglutarate under conditions of nitrogen excess. These findings are in accord with our recent in vitro observations (R. Little, F. Reyes-Ramirez, Y. Zhang, W. Van Heeswijk, and R. Dixon, EMBO J. 19:6041–6050, 2000) and suggest a model in which nitrogen control of the A. vinelandii NifL-NifA system is achieved through the response to the level of 2-oxoglutarate and an interaction with PII-like proteins under conditions of nitrogen excess.

scholarly journals Characterization of the Roles of Hemolysin and Other Toxins in Enteropathy Caused by Alpha-Hemolytic Escherichia coli Linked to Human Diarrhea

1998 ◽  
Vol 66 (5) ◽  
pp. 2040-2051 ◽  
Author(s):  
Simon J. Elliott ◽  
S. Srinivas ◽  
M. John Albert ◽  
Khorshed Alam ◽  
Roy M. Robins-Browne ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Virulence Factors ◽  
Virulence Factor ◽  
Adult Rabbit ◽  
Cell Hyperplasia ◽  
E Coli ◽  
Alpha Hemolysin ◽  
A Cell ◽  
Cytotoxic Necrotizing Factor 1

ABSTRACT Escherichia coli strains producing alpha-hemolysin have been associated with diarrhea in several studies, but it has not been clearly demonstrated that these strains are enteropathogens or that alpha-hemolysin is an enteric virulence factor. Such strains are generally regarded as avirulent commensals. We examined a collection of diarrhea-associated hemolytic E. coli (DHEC) strains for virulence factors. No strain produced classic enterotoxins, but they all produced an alpha-hemolysin that was indistinguishable from that of uropathogenic E. coli strains. DHEC strains also produced other toxins including cytotoxic necrotizing factor 1 (CNF1) and novel toxins, including a cell-detaching cytotoxin and a toxin that causes HeLa cell elongation. DHEC strains were enteropathogenic in the RITARD (reversible intestinal tie adult rabbit diarrhea) model of diarrhea, causing characteristic enteropathies, including inflammation, necrosis, and colonic cell hyperplasia in both small and large intestines. Alpha-hemolysin appeared to be a major virulence factor in this model since it conferred virulence to nonpathogenic E. colistrains. Other virulence factors also appear to be contributing to virulence. These findings support the epidemiologic link to diarrhea and suggest that further research into the role of DHEC and alpha-hemolysin in enteric disease is warranted.

Detection of C-P-lyase activity in a cell-free extract of Escherichia coli

2007 ◽  
Vol 43 (4) ◽  
pp. 394-398 ◽  
Author(s):  
S. V. Kononova ◽  
S. M. Trutko ◽  
K. S. Laurinavichus
Keyword(s):  
Escherichia Coli ◽  
Cell Free Extract ◽  
Lyase Activity ◽  
A Cell

scholarly journals Multicellular Stalk-Like Structures inSaccharomyces cerevisiae

1998 ◽  
Vol 180 (15) ◽  
pp. 3992-3996 ◽  
Author(s):  
David Engelberg ◽  
Avishai Mimran ◽  
Horacio Martinetto ◽  
Joel Otto ◽  
Giora Simchen ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Signal Transduction ◽  
Cell Polarity ◽  
Physiological Role ◽  
Yeast Cells ◽  
Large Numbers ◽  
Uv Response ◽  
Elevated Frequency ◽  
Yeast Mutants

ABSTRACT Stalk formation is a novel pattern of multicellular organization. Yeast cells which survive UV irradiation form colonies that grow vertically to form very long (0.5 to 3.0 cm) and thin (0.5 to 4 mm in diameter) multicellular structures. We describe the conditions required to obtain these stalk-like structures reproducibly in large numbers. Yeast mutants, mutated for control of cell polarity, developmental processes, UV response, and signal transduction cascades were tested and found capable of forming stalk-like structures. We suggest a model that explains the mechanism of stalk formation by mechanical environmental forces. We show that other microorganisms (Candida albicans, Schizosaccharomyces pombe, andEscherichia coli) also form stalks, suggesting that the ability to produce stalks may be a general property of microorganisms. Diploid yeast stalks sporulate at an elevated frequency, raising the possibility that the physiological role of stalks might be disseminating spores.

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