scholarly journals FunctionalDomains of the RhlR Transcriptional Regulator ofPseudomonasaeruginosa

2003 ◽  
Vol 185 (24) ◽  
pp. 7129-7139 ◽  
Author(s):  
Janet R. Lamb ◽  
Hetal Patel ◽  
Timothy Montminy ◽  
Victoria E. Wagner ◽  
Barbara H. Iglewski
Keyword(s):  
Amino Acid ◽  
Transcriptional Activation ◽  
Gene Activation ◽  
Transcriptional Regulator ◽  
Homoserine Lactone ◽  
Single Amino Acid ◽  
Amino Acid Substitutions ◽  
Mutant Form ◽  
E Coli ◽  
Terminal Domain

ABSTRACT The RhlR transcriptional regulator of Pseudomonas aeruginosa, along with its cognate autoinducer, N-butyryl homoserine lactone (C4-HSL), regulates gene expression in response to cell density. With an Escherichia coli LexA-based protein interaction system, we demonstrated that RhlR multimerized and that the degree of multimerization was dependent on the C4-HSL concentration. Studies with an E. coli lasB::lacZ lysogen demonstrated that RhlR multimerization was necessary for it to function as a transcriptional activator. Deletion analysis of RhlR indicated that the N-terminal domain of the protein is necessary for C4-HSL binding. Single amino acid substitutions in the C-terminal domain of RhlR generated mutant RhlR proteins that had the ability to bind C4-HSL and multimerize but were unable to activate lasB expression, demonstrating that the C-terminal domain is important for target gene activation. Single amino acid substitutions in both the N-terminal and C-terminal domains of RhlR demonstrated that both domains possess residues involved in multimerization. RhlR with a C-terminal deletion and an RhlR site-specific mutant form that possessed multimerization but not transcriptional activation capabilities were able to inhibit the ability of wild-type RhlR to activate rhlA expression in P. aeruginosa. We conclude that C4-HSL binding is necessary for RhlR multimerization and that RhlR functions as a multimer in P. aeruginosa.

scholarly journals 698. Nacubactam Inhibits Class A β-lactamases

2018 ◽  
Vol 5 (suppl_1) ◽  
pp. S251-S252
Author(s):  
Melissa D Barnes ◽  
Caryn E Good ◽  
Saralee Bajaksouzian ◽  
Magdalena A Taracila ◽  
David Van Duin ◽  
...  
Keyword(s):  
Amino Acid ◽  
Single Amino Acid ◽  
Amino Acid Substitutions ◽  
E Coli ◽  
Class A ◽  
Cell Extracts ◽  
Fixed Concentration ◽  
Genes Encoding ◽  
Inactivation Mechanism ◽  
Research Grant

Abstract Background Nacubactam, formerly RG6080 and OP0595 (Figure 1A), is a bridged diazabicyclooctane (DBO) that inactivates class A and class C β-lactamases. Unlike avibactam, the DBO that is approved for use in combination with ceftazidime, nacubactam also inhibits penicillin binding proteins (i.e., PBP2) in Enterobacteriaceae. We set out to determine the effectiveness of meropenem-nacubactam against Klebsiella pneumoniae clinical strains and to elucidate the structure–function relationships. Methods Minimal inhibitory concentration (MIC) measurements using broth microdilution according to Clinical and Laboratory Standards Institute for meropenem (MERO) ± nacubactam (fixed concentration of 4 mg/L or fixed 1:1 ratio) was performed on 50 clinical K. pneumoniae strains (6 having OXA-48-like β-lactamases and 44 harboring KPC-2 or KPC-3) and 47 isogenic Escherichia coli strains harboring bla genes encoding K. pneumoniae carbapenemase (KPC) variants with single amino acid substitutions in residues that are involved in catalysis. IC50s for selected KPC-2 variants were determined on periplasmic extracts with varying concentrations of nacubactam using nitrocefin as a reporter substrate. Results The MERO combinations with either 4 mg/L or a 1:1 ratio of nacubactam effectively lowered the MERO MICs of K. pneumoniae strains (Figure 1B). Similarly, all E. coli strains expressing blaKPC-2 variants were susceptible to the MERO-nacubactam combinations based on the breakpoint of MERO. The strains harboring K73R, S130G, and K234R had slightly elevated MERO-nacubactam MICs relative to wild type but did not have corresponding increases in MERO MICs. Strains with pBC SK-KPC2, K73R or S130G had 0.015 mg/L MERO MICs. The pBR322-K234R strain had a twofold lower MERO MIC than pBR322-KPC-2 (Figure 1C). The IC50 of cell extracts containing the K234R variant is 781 µM, which is 12-fold higher than that for KPC-2 (66 µM) (Figure 1C). Extracts containing the S130G variant were not inhibited by nacubactam (IC50 > 2.6 mM). Conclusion Meropenem-nacubactam is an effective β-lactam β-lactamase inhibitor combination for Enterobacteriaceae with KPC or OXA-48 β-lactamases. The single amino acid substitutions K73R, S130G, and K234R in KPC-2 affect the inactivation mechanism. Disclosures M. R. Jacobs, F. Hoffmann-La Roche Ltd.: Grant Investigator, Research grant. K. M. Papp-Wallace, F. Hoffmann-La Roche Ltd.: Grant Investigator, Research grant. R. A. Bonomo, F. Hoffmann-La Roche Ltd.: Grant Investigator, Research grant.

scholarly journals Mutational Analysis of the Escherichia coli melR Gene Suggests a Two-State Concerted Model To Explain Transcriptional Activation and Repression in the Melibiose Operon

2006 ◽  
Vol 188 (9) ◽  
pp. 3199-3207 ◽  
Author(s):  
Christina Kahramanoglou ◽  
Christine L. Webster ◽  
Mohamed Samir el-Robh ◽  
Tamara A. Belyaeva ◽  
Stephen J. W. Busby
Keyword(s):  
Escherichia Coli ◽  
Amino Acid ◽  
Hybrid System ◽  
Transcriptional Activation ◽  
Mutational Analysis ◽  
Single Amino Acid ◽  
Amino Acid Substitutions ◽  
Supporting Evidence ◽  
Conformational States ◽  
Two Hybrid

ABSTRACT Transcription of the Escherichia coli melAB operon is regulated by the MelR protein, an AraC family member whose activity is modulated by the binding of melibiose. In the absence of melibiose, MelR is unable to activate the melAB promoter but autoregulates its own expression by repressing the melR promoter. Melibiose triggers MelR-dependent activation of the melAB promoter and relieves MelR-dependent repression of the melR promoter. Twenty-nine single amino acid substitutions in MelR that result in partial melibiose-independent activation of the melAB promoter have been identified. Combinations of different substitutions result in almost complete melibiose-independent activation of the melAB promoter. MelR carrying each of the single substitutions is less able to repress the melR promoter, while MelR carrying some combinations of substitutions is completely unable to repress the melR promoter. These results argue that different conformational states of MelR are responsible for activation of the melAB promoter and repression of the melR promoter. Supporting evidence for this is provided by the isolation of substitutions in MelR that block melibiose-dependent activation of the melAB promoter while not changing melibiose-independent repression of the melR promoter. Additional experiments with a bacterial two-hybrid system suggest that interactions between MelR subunits differ according to the two conformational states.

scholarly journals Mutational Analysis of the Transcriptional Regulator GcvA: Amino Acids Important for Activation, Repression, and DNA Binding

1998 ◽  
Vol 180 (18) ◽  
pp. 4865-4871 ◽  
Author(s):  
Alissa D. Jourdan ◽  
George V. Stauffer
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Dna Binding ◽  
Mutational Analysis ◽  
Transcriptional Regulator ◽  
Single Amino Acid ◽  
Amino Acid Substitutions ◽  
Constitutive Activation ◽  
Carboxy Terminal

ABSTRACT The GcvA protein is required for both glycine-mediated activation and purine-mediated repression of the gcvTHP operon. Random and site-directed PCR mutagenesis was used to create nucleotide changes in gcvA to identify residues of the protein involved in activation, repression, and DNA binding. Single amino acid substitutions at L30 and F31 cause a defect in activation of agcvT-lacZ fusion but have no effect on repression or DNA binding. Single amino acid substitutions at V32 and S38 cause the loss of binding of GcvA to DNA. A deletion of the carboxy-terminal 14 amino acids of GcvA results in the loss of purine-mediated repression and, consequently, a constitutive activation of a gcvT-lacZfusion. The results of this study partially define regions of GcvA involved in activation, repression, and DNA binding and demonstrate that these functions of GcvA are genetically separable.

scholarly journals A Single Point Mutation, Asn16→Lys, Dictates the Temperature-Sensitivity of the Reovirus tsG453 Mutant

Viruses ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 289
Author(s):  
Kathleen K. M. Glover ◽  
Danica M. Sutherland ◽  
Terence S. Dermody ◽  
Kevin M. Coombs
Keyword(s):  
Amino Acid ◽  
Temperature Sensitivity ◽  
Reverse Genetics ◽  
Core Protein ◽  
Single Point ◽  
Single Amino Acid ◽  
Single Point Mutation ◽  
Temperature Sensitive ◽  
Amino Acid Substitutions ◽  
Gene Encoding

Studies of conditionally lethal mutants can help delineate the structure-function relationships of biomolecules. Temperature-sensitive (ts) mammalian reovirus (MRV) mutants were isolated and characterized many years ago. Two of the most well-defined MRV ts mutants are tsC447, which contains mutations in the S2 gene encoding viral core protein σ2, and tsG453, which contains mutations in the S4 gene encoding major outer-capsid protein σ3. Because many MRV ts mutants, including both tsC447 and tsG453, encode multiple amino acid substitutions, the specific amino acid substitutions responsible for the ts phenotype are unknown. We used reverse genetics to recover recombinant reoviruses containing the single amino acid polymorphisms present in ts mutants tsC447 and tsG453 and assessed the recombinant viruses for temperature-sensitivity by efficiency-of-plating assays. Of the three amino acid substitutions in the tsG453 S4 gene, Asn16-Lys was solely responsible for the tsG453ts phenotype. Additionally, the mutant tsC447 Ala188-Val mutation did not induce a temperature-sensitive phenotype. This study is the first to employ reverse genetics to identify the dominant amino acid substitutions responsible for the tsC447 and tsG453 mutations and relate these substitutions to respective phenotypes. Further studies of other MRV ts mutants are warranted to define the sequence polymorphisms responsible for temperature sensitivity.

The Yeast Protein Complex Containing Cdc68 and Pob3 Mediates Core-Promoter Repression Through the Cdc68 N-Terminal Domain

Genetics ◽  
1998 ◽  
Vol 150 (4) ◽  
pp. 1393-1405 ◽  
Author(s):  
David R H Evans ◽  
Neil K Brewster ◽  
Qunli Xu ◽  
Adele Rowley ◽  
Brent A Altheim ◽  
...  
Keyword(s):  
Core Promoter ◽  
Kluyveromyces Lactis ◽  
Gene Activation ◽  
Mutant Form ◽  
Nuclear Complex ◽  
Terminal Domain ◽  
Chromatin Remodeling Complex ◽  
Functional Homolog ◽  
Repression Domain ◽  
Independent Mutant

Abstract Transcription of nuclear genes usually involves trans-activators, whereas repression is exerted by chromatin. For several genes the transcription mediated by trans-activators and the repression mediated by chromatin depend on the CP complex, a recently described abundant yeast nuclear complex of the Pob3 and Cdc68/Spt16 proteins. We report that the N-terminal third of the Saccharomyces cerevisiae Cdc68 protein is dispensable for gene activation but necessary for the maintenance of chromatin repression. The absence of this 300-residue N-terminal domain also decreases the need for the Swi/Snf chromatin-remodeling complex in transcription and confers an Spt- effect characteristic of chromatin alterations. The repression domain, and indeed the entire Cdc68 protein, is highly conserved, as shown by the sequence of the Cdc68 functional homolog from the yeast Kluyveromyces lactis and by database searches. The repression-defective (truncated) form of Cdc68 is stable but less active at high temperatures, whereas the known point-mutant form of Cdc68, encoded by three independent mutant alleles, alters the N-terminal repression domain and destabilizes the mutant protein.

scholarly journals Natural variants in SARS-CoV-2 Spike protein pinpoint structural and functional hotspots with implications for prophylaxis and therapeutic strategies

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Suman Pokhrel ◽  
Benjamin R. Kraemer ◽  
Scott Burkholz ◽  
Daria Mochly-Rosen
Keyword(s):  
Amino Acid ◽  
Severe Disease ◽  
Single Amino Acid ◽  
Amino Acid Substitutions ◽  
Severe Respiratory Distress ◽  
S Protein ◽  
Individual Sequences ◽  
Natural Variants ◽  
Novel Coronavirus ◽  
The Individual

AbstractIn December 2019, a novel coronavirus, termed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was identified as the cause of pneumonia with severe respiratory distress and outbreaks in Wuhan, China. The rapid and global spread of SARS-CoV-2 resulted in the coronavirus 2019 (COVID-19) pandemic. Earlier during the pandemic, there were limited genetic viral variations. As millions of people became infected, multiple single amino acid substitutions emerged. Many of these substitutions have no consequences. However, some of the new variants show a greater infection rate, more severe disease, and reduced sensitivity to current prophylaxes and treatments. Of particular importance in SARS-CoV-2 transmission are mutations that occur in the Spike (S) protein, the protein on the viral outer envelope that binds to the human angiotensin-converting enzyme receptor (hACE2). Here, we conducted a comprehensive analysis of 441,168 individual virus sequences isolated from humans throughout the world. From the individual sequences, we identified 3540 unique amino acid substitutions in the S protein. Analysis of these different variants in the S protein pinpointed important functional and structural sites in the protein. This information may guide the development of effective vaccines and therapeutics to help arrest the spread of the COVID-19 pandemic.

scholarly journals A single amino acid substitution in the Ω-like loop of E. coli PBP5 disrupts its ability to maintain cell shape and intrinsic beta-lactam resistance

Microbiology ◽  
2015 ◽  
Vol 161 (4) ◽  
pp. 895-902 ◽  
Author(s):  
Mouparna Dutta ◽  
Debasish Kar ◽  
Ankita Bansal ◽  
Sandeep Chakraborty ◽  
Anindya S. Ghosh
Keyword(s):  
Amino Acid ◽  
Amino Acid Substitution ◽  
Cell Shape ◽  
Single Amino Acid Substitution ◽  
Single Amino Acid ◽  
Beta Lactam ◽  
E Coli
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