Cold inactivation and dissociation into dimers of Escherichia coli tryptophanase and its W330F mutant form

1998 ◽  
Vol 1384 (2) ◽  
pp. 365-372 ◽  
Author(s):  
Tali Erez ◽  
Garik Ya. Gdalevsky ◽  
Yuri M. Torchinsky ◽  
Robert S. Phillips ◽  
Abraham H. Parola
Keyword(s):  
Escherichia Coli ◽  
Mutant Form ◽  
Cold Inactivation

scholarly journals Increased Hydrolysis of Oximino-β-Lactams by CMY-107, a Tyr199Cys Mutant Form of CMY-2 Produced by Escherichia coli

2015 ◽  
Vol 59 (12) ◽  
pp. 7894-7898 ◽  
Author(s):  
S. D. Kotsakis ◽  
V. Miriagou ◽  
E. E. Vetouli ◽  
E. Bozavoutoglou ◽  
E. Lebessi ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Clinical Strain ◽  
Mutant Form ◽  
Content Type ◽  
Hydrolysis Of

ABSTRACTThe cephalosporinase CMY-107, a Tyr199Cys mutant form of CMY-2 encoded by an IncI self-transferable plasmid carried by anEscherichia coliclinical strain, was characterized. The enzyme hydrolyzed oximino-cephalosporins and aztreonam more efficiently than CMY-2 did.

Stabilities of uncomplemented and complemented M15 β-galactosidase (Escherichia coli) and the relationship to α-complementation

1999 ◽  
Vol 77 (2) ◽  
pp. 109-118 ◽  
Author(s):  
Clare N Gallagher ◽  
Reuben E Huber
Keyword(s):  
Escherichia Coli ◽  
Key Words ◽  
Thermal Inactivation ◽  
Quaternary Structure ◽  
Mutant Form ◽  
Narrow Temperature Range ◽  
Preferential Binding ◽  
High Concentrations ◽  
The Relationship ◽  
Tetrameric Form

M15 β-galactosidase (Escherichia coli) is a mutant form of β-galactosidase having residues 11-41 deleted. It is an inactive dimer but can be complemented to the active tetrameric form by the addition of a peptide containing the deleted residues. The activities of uncomplemented and complemented M15 β-galactosidases decreased starting at 42°C-uncomplemented over a narrow temperature range, complemented over a broad range. This is because uncomplemented protein is a simple dimer while complemented is a mix of interacting oligomers at high temperatures. The effects of added components on stability and α-complementation are best explained by binding effects on equilibria between native forms and forms susceptible to inactivation. Mg2+ stabilized complemented protein but destabilized uncomplemented protein (10× less Mg2+ was needed for complemented protein). α-Complementation increased somewhat at low Mg2+ but decreased at high Mg2+. These effects can be explained by differential Mg2+ binding to the native and susceptible forms. The enhancement of both stability and α-complementation by Na+ can be explained by preferential binding of Na+ to the native forms of both the uncomplemented and complemented proteins. Low 2-mercaptoethanol concentrations stabilized uncomplemented M15 β-galactosidase, but high concentrations destabilized it. All concentrations destabilized complemented M15 β-galactosidase. α-Complementation was enhanced by 2-mercaptoethanol. Thus, there is a correlation between stability of the uncomplemented protein and α-complementation at low 2-mercaptoethanol owing to interactions with native forms. The lack of correlation at higher 2-mercaptoethanol probably results from precipitation by 2-mercaptoethanol. In contrast to irreversible thermal inactivation, differences in reversible stability in urea were small. This suggests that quaternary structure and Mg2+ and Na+ sites are lost at low urea concentrations and are unimportant at the urea concentrations that result in reversible denaturation. Key words: β-galactosidase, α-complementation, stability.

scholarly journals Nybomycin Inhibits both Fluoroquinolone-Sensitive and Fluoroquinolone-Resistant Escherichia coli DNA Gyrase

2021 ◽  
Vol 65 (5) ◽  
Author(s):  
Dmitrii I. Shiriaev ◽  
Alina A. Sofronova ◽  
Ekaterina A. Berdnikovich ◽  
Dmitrii A. Lukianov ◽  
Ekaterina S. Komarova ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Bacterial Species ◽  
Dna Gyrase ◽  
Resistant Bacteria ◽  
Mutant Form ◽  
Wild Type ◽  
Topoisomerase Iv ◽  
Gram Positive ◽  
Gram Negative ◽  
Content Type

ABSTRACT Bacterial type II topoisomerases, DNA gyrase and topoisomerase IV, are targets of many antibiotics, including fluoroquinolones (FQs). Unfortunately, a number of bacterial species easily acquire resistance to FQs by mutations in either DNA gyrase or topoisomerase IV genes. The emergence of resistant pathogenic strains is a global problem in health care; therefore, identifying alternative pathways to thwart their persistence is the current frontier in drug discovery. Nybomycins are an attractive class of compounds, reported to be “reverse antibiotics” that selectively inhibit growth of some Gram-positive FQ-resistant bacteria by targeting the mutant form of DNA gyrase while being inactive against wild-type strains with FQ-sensitive gyrases. The strong “reverse” effect was demonstrated only for a few Gram-positive organisms resistant to FQs due to the S83L/I mutation in the GyrA subunit of DNA gyrase. However, the activity of nybomycins has not been extensively explored among Gram-negative species. Here, we observed that in a ΔtolC strain of the Gram-negative Escherichia coli with enhanced permeability, wild-type gyrase and a GyrA S83L mutant, resistant to fluoroquinolones, are similarly sensitive to nybomycin.

Stimulation of Escherichia coli adenylate cyclase by lactose in strains carrying mutations in lactose permease

1981 ◽  
Vol 1 (1) ◽  
pp. 53-60 ◽  
Author(s):  
Alan Peterkofsky ◽  
Celia Gazdar
Keyword(s):  
Escherichia Coli ◽  
Type Strain ◽  
Wild Type Strain ◽  
Specific Activity ◽  
Inhibitory Effect ◽  
Lactose Permease ◽  
Mutant Form ◽  
Wild Type ◽  
Camp Phosphodiesterase ◽  
Intact Cells

When a wild-type strain of Escherichia coli contains lactose permease, the accumulation of cyclic AMP (cAMP) by intact cells is inhibited by lactose. This inhibitory effect of lactose is observed in a strain with a mutant cAMP phosphodiesterase and therefore involves a regulation of adenylate cyctase activity. Some E. coli strains carrying mutations in lactose permease show an effect opposite to that of the wild-type strain; the accumulation of cAMP by intact cells is stimulated by lactose, but only when the mutant permease is present. Insertion of lactose permease into the membrane of ceils can produce a change in the specific activity of adenylate cycIase; induction of the wild-type transporter is correlated with a decrease in the specific activity, while implantation of a mutant form of lactose permease can lead to an increase in the specific activity. From these data, it is suggested that the state of the lactose transporter in the cell membrane influences the activity of adenytate cyclase.

scholarly journals Role of Escherichia coli DNA Polymerase I in Conferring Viability upon the dnaN159 Mutant Strain

2007 ◽  
Vol 189 (13) ◽  
pp. 4688-4695 ◽  
Author(s):  
Robert W. Maul ◽  
Laurie H. Sanders ◽  
James B. Lim ◽  
Rosemary Benitez ◽  
Mark D. Sutton
Keyword(s):  
Escherichia Coli ◽  
Dna Polymerase ◽  
Temperature Sensitive ◽  
Mutant Form ◽  
Sliding Clamp ◽  
Pol I ◽  
Pol Iii ◽  
Polymerase I

ABSTRACT The Escherichia coli dnaN159 allele encodes a mutant form of the β-sliding clamp (β159) that is impaired for interaction with the replicative DNA polymerase (Pol), Pol III. In addition, strains bearing the dnaN159 allele require functional Pol I for viability. We have utilized a combination of genetic and biochemical approaches to characterize the role(s) played by Pol I in the dnaN159 strain. Our findings indicate that elevated levels of Pol I partially suppress the temperature-sensitive growth phenotype of the dnaN159 strain. In addition, we demonstrate that the β clamp stimulates the processivity of Pol I in vitro and that β159 is impaired for this activity. The reduced ability of β159 to stimulate Pol I in vitro correlates with our finding that single-stranded DNA (ssDNA) gap repair is impaired in the dnaN159 strain. Taken together, these results suggest that (i) the β clamp-Pol I interaction may be important for proper Pol I function in vivo and (ii) in the absence of Pol I, ssDNA gaps may persist in the dnaN159 strain, leading to lethality of the dnaN159 ΔpolA strain.

Localization of two domains of a mutant form of Escherichia coli protein L7/L12 that binds the large ribosomal subunit as a single dimer

Biochimie ◽  
1997 ◽  
Vol 79 (6) ◽  
pp. 365-372 ◽  
Author(s):  
R.J. Wiggers ◽  
H. Hadian ◽  
R.R. Traut ◽  
A.V. Oleinikov ◽  
D.G. Glitz
Keyword(s):  
Escherichia Coli ◽  
Ribosomal Subunit ◽  
Mutant Form ◽  
Large Ribosomal Subunit
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