scholarly journals Characterization of a new TEM-derived beta-lactamase produced in a Serratia marcescens strain.

1997 ◽  
Vol 41 (11) ◽  
pp. 2374-2382 ◽  
Author(s):  
M Perilli ◽  
A Felici ◽  
N Franceschini ◽  
A De Santis ◽  
L Pagani ◽  
...  
Keyword(s):  
Serratia Marcescens ◽  
Three Dimensional ◽  
Point Mutations ◽  
Catalytic Efficiency ◽  
Point Of View ◽  
Multiple Point ◽  
Crystallographic Structure ◽  
Beta Lactamase

A natural TEM variant beta-lactamase was isolated from an epidemic strain of Serratia marcescens. Nucleotide gene sequencing revealed multiple point mutations located in the 42-to-44 tripeptide and positions 145 to 146, 178, and 238. In addition, a glutamic acid 212 deletion was also found. The purified enzyme was studied from a kinetic point of view, revealing the highest catalytic efficiency (k[cat]/Km) values for ceftazidime and aztreonam compared with the TEM-1 prototype enzyme. The in vitro resistance correlated with kinetic parameters, and the enzyme also mediated resistance to some penicillins and an ampicillin-clavulanic acid combination. The mutational and kinetic changes are discussed in relation to the three-dimensional crystallographic structure of the wild-type TEM-1 enzyme.

scholarly journals Characterization of a Cytotoxic Factor in Culture Filtrates of Serratia marcescens

2002 ◽  
Vol 70 (3) ◽  
pp. 1121-1128 ◽  
Author(s):  
Kent B. Marty ◽  
Christopher L. Williams ◽  
Linda J. Guynn ◽  
Michael J. Benedik ◽  
Steven R. Blanke
Keyword(s):  
Cytotoxic Activity ◽  
Serratia Marcescens ◽  
Mammalian Cells ◽  
Divalent Cations ◽  
Recombinant Expression ◽  
Cytotoxic Factor ◽  
Culture Filtrates ◽  
Type Strains

ABSTRACT Serratia marcescens culture filtrates have been reported to be cytotoxic to mammalian cells. Using biochemical and genetic approaches, we have identified a major source of this cytotoxic activity. Both heat and protease treatments abrogated the cytotoxicity of S. marcescens culture filtrates towards HeLa cells, suggesting the involvement of one or more protein factors. A screen for in vitro cytotoxic activity revealed that S. marcescens mutant strains that are deficient in production of a 56-kDa metalloprotease are significantly less cytotoxic to mammalian cells. Cytotoxicity was significantly reduced when culture filtrates prepared from wild-type strains were pretreated with either EDTA or 1,10-phenanthroline, which are potent inhibitors of the 56-kDa metalloprotease. Furthermore, cytotoxic activity was restored when the same culture filtrates were incubated with zinc divalent cations, which are essential for enzymatic activity of the 56-kDa metalloprotease. Finally, recombinant expression of the S. marcescens 56-kDa metalloprotease conferred a cytotoxic phenotype on the culture filtrates of a nonpathogenic Escherichia coli strain. Collectively, these data suggest that the 56-kDa metalloprotease contributes significantly to the in vitro cytotoxic activity commonly observed in S. marcescens culture filtrates.

scholarly journals In Vitro Selection and Characterization of Hepatitis C Virus Serine Protease Variants Resistant to an Active-Site Peptide Inhibitor

2003 ◽  
Vol 77 (6) ◽  
pp. 3669-3679 ◽  
Author(s):  
Caterina Trozzi ◽  
Linda Bartholomew ◽  
Alessandra Ceccacci ◽  
Gabriella Biasiol ◽  
Laura Pacini ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Serine Protease ◽  
In Vitro Selection ◽  
Three Dimensional ◽  
Host Cells ◽  
Dimensional Structure ◽  
In Vitro Systems

ABSTRACT The hepatitis C virus (HCV) serine protease is necessary for viral replication and represents a valid target for developing new therapies for HCV infection. Potent and selective inhibitors of this enzyme have been identified and shown to inhibit HCV replication in tissue culture. The optimization of these inhibitors for clinical development would greatly benefit from in vitro systems for the identification and the study of resistant variants. We report the use HCV subgenomic replicons to isolate and characterize mutants resistant to a protease inhibitor. Taking advantage of the replicons' ability to transduce resistance to neomycin, we selected replicons with decreased sensitivity to the inhibitor by culturing the host cells in the presence of the inhibitor and neomycin. The selected replicons replicated to the same extent as those in parental cells. Sequence analysis followed by transfection of replicons containing isolated mutations revealed that resistance was mediated by amino acid substitutions in the protease. These results were confirmed by in vitro experiments with mutant enzymes and by modeling the inhibitor in the three-dimensional structure of the protease.

scholarly journals Purification and In Vitro Characterization of the Serratia marcescens NucC Protein, a Zinc-Binding Transcription Factor Homologous to P2 Ogr

2003 ◽  
Vol 185 (6) ◽  
pp. 1808-1816 ◽  
Author(s):  
Victor McAlister ◽  
Chao Zou ◽  
Robert H. Winslow ◽  
Gail E. Christie
Keyword(s):  
Rna Polymerase ◽  
Serratia Marcescens ◽  
Specific Binding ◽  
Protein A ◽  
Upstream Region ◽  
Late Gene Expression ◽  
In Vitro Characterization ◽  
Template Dna

ABSTRACT NucC is structurally and functionally homologous to a family of prokaryotic zinc finger transcription factors required for late gene expression in P2- and P4-related bacteriophages. Characterization of these proteins in vitro has been hampered by their relative insolubility and tendency to aggregate. We report here the successful purification of soluble, active, wild-type NucC protein. Purified NucC exhibits site-specific binding to a conserved DNA sequence that is located upstream of NucC-dependent Serratia marcescens promoters and the late promoters of P2-related phages. This sequence is sufficient for binding of NucC in vitro. NucC binding to the S. marcescens nuclease promoter P nucA and to the sequence upstream of the P2 late promoter P F is accompanied by DNA bending. NucC protects about 25 nucleotides of the P F upstream region from DNase I digestion, and RNA polymerase protects the promoter region only in the presence of NucC. Template DNA, RNA polymerase holoenzyme, and purified NucC are the only macromolecular components required for transcription from P F in vitro.

scholarly journals Characterization of Spontaneous, In Vitro-Selected, Rifampin-Resistant Mutants of Mycobacterium tuberculosisStrain H37Rv

2000 ◽  
Vol 44 (12) ◽  
pp. 3298-3301 ◽  
Author(s):  
Glenn P. Morlock ◽  
Bonnie B. Plikaytis ◽  
Jack T. Crawford
Keyword(s):  
Point Mutations ◽  
Laboratory Strain ◽  
Resistant Mutant ◽  
Small Region ◽  
Clinical Isolates ◽  
Gene Coding ◽  
Resistant Mutants ◽  
Strain H37rv

ABSTRACT Resistance to rifampin in Mycobacterium tuberculosisresults from mutations in the gene coding for the beta subunit of RNA polymerase (rpoB). At least 95% of rifampin-resistant isolates have mutations in rpoB, and the mutations are clustered in a small region. About 40 distinct point mutations and in-frame insertions and deletions in rpoB have been identified, but point mutations in two codons, those coding for Ser531 and His526, are seen in about 70% of rifampin-resistant clinical isolates, with Ser531-to-Leu (TCG-to-TGG) mutations being by far the most common. To explore this phenomenon, we isolated independent, spontaneous, rifampin-resistant mutant versions of well-characterized M. tuberculosislaboratory strain H37Rv by plating 100 separate cultures, derived from a single low-density inoculum, onto rifampin-containing medium. Rifampin-resistant mutants were obtained from 64 of these cultures. Although we anticipated that the various point mutations would occur with approximately equal frequencies, sequencing the rpoBgene from one colony per plate revealed that 39 (60.9%) were Ser531 to Leu. We conclude that, for unknown reasons, the associated rpoB mutation occurs at a substantially higher rate than other rpoB mutations. This higher mutation rate may contribute to the high percentage of this mutation seen in clinical isolates.

scholarly journals Structural toggle in the RNaseH domain of Prp8 helps balance splicing fidelity and catalytic efficiency

2017 ◽  
Vol 114 (18) ◽  
pp. 4739-4744 ◽  
Author(s):  
Megan Mayerle ◽  
Madhura Raghavan ◽  
Sarah Ledoux ◽  
Argenta Price ◽  
Nicholas Stepankiw ◽  
...  
Keyword(s):  
High Efficiency ◽  
Catalytic Efficiency ◽  
Mrna Splicing ◽  
Catalytic Core ◽  
Eukaryotic Gene ◽  
Functional Classes ◽  
Reporter Assays

Pre-mRNA splicing is an essential step of eukaryotic gene expression that requires both high efficiency and high fidelity. Prp8 has long been considered the “master regulator” of the spliceosome, the molecular machine that executes pre-mRNA splicing. Cross-linking and structural studies place the RNaseH domain (RH) of Prp8 near the spliceosome’s catalytic core and demonstrate that prp8 alleles that map to a 17-aa extension in RH stabilize it in one of two mutually exclusive structures, the biological relevance of which are unknown. We performed an extensive characterization of prp8 alleles that map to this extension and, using in vitro and in vivo reporter assays, show they fall into two functional classes associated with the two structures: those that promote error-prone/efficient splicing and those that promote hyperaccurate/inefficient splicing. Identification of global locations of endogenous splice-site activation by lariat sequencing confirms the fidelity effects seen in our reporter assays. Furthermore, we show that error-prone/efficient RH alleles suppress a prp2 mutant deficient at promoting the first catalytic step of splicing, whereas hyperaccurate/inefficient RH alleles exhibit synthetic sickness. Together our data indicate that prp8 RH alleles link splicing fidelity with catalytic efficiency by biasing the relative stabilities of distinct spliceosome conformations. We hypothesize that the spliceosome “toggles” between such error-prone/efficient and hyperaccurate/inefficient conformations during the splicing cycle to regulate splicing fidelity.

scholarly journals S. mansoni SmKI-1 Kunitz-domain: Leucine point mutation at P1 site generates enhanced neutrophil elastase inhibitory activity

2021 ◽  
Vol 15 (1) ◽  
pp. e0009007
Author(s):  
Fábio Mambelli ◽  
Bruno P. O. Santos ◽  
Suellen B. Morais ◽  
Enrico G. T. Gimenez ◽  
Duana C. dos S. Astoni ◽  
...  
Keyword(s):  
Inhibitory Activity ◽  
Neutrophil Elastase ◽  
Point Mutations ◽  
Point Of View ◽  
Mutant Proteins ◽  
Inflammatory Parameters ◽  
C Terminus ◽  
Kunitz Domain

The Schistosoma mansoni SmKI-1 protein is composed of two domains: a Kunitz-type serine protease inhibitor motif (KD) and a C-terminus domain with no similarity outside the genera. Our previous work has demonstrated that KD plays an essential role in neutrophil elastase (NE) binding blockage, in neutrophil influx and as a potential anti-inflammatory molecule. In order to enhance NE blocking capacity, we analyzed the KD sequence from a structure-function point of view and designed specific point mutations in order to enhance NE affinity. We substituted the P1 site residue at the reactive site for a leucine (termed RL-KD), given its central role for KD’s inhibition to NE. We have also substituted a glutamic acid that strongly interacts with the P1 residue for an alanine, to help KD to be buried on NE S1 site (termed EA-KD). KD and the mutant proteins were evaluated in silico by molecular docking to human NE, expressed in Escherichia coli and tested towards its NE inhibitory activity. Both mutated proteins presented enhanced NE inhibitory activity in vitro and RL-KD presented the best performance. We further tested RL-KD in vivo in an experimental model of monosodium urate (MSU)-induced acute arthritis. RL-KD showed reduced numbers of total cells and neutrophils in the mouse knee cavity when compared to KD. Nevertheless, both RL-KD and KD reduced mice hypernociception in a similar fashion. In summary, our results demonstrated that both mutated proteins showed enhanced NE inhibitory activity in vitro. However, RL-KD had a prominent effect in diminishing inflammatory parameters in vivo.

scholarly journals Functional Characterization of Three-Dimensional Cortical Cultures for In Vitro Modeling of Brain Networks

iScience ◽  
2020 ◽  
Vol 23 (8) ◽  
pp. 101434
Author(s):  
Yu-Ting L. Dingle ◽  
Volha Liaudanskaya ◽  
Liam T. Finnegan ◽  
Kyler C. Berlind ◽  
Craig Mizzoni ◽  
...  
Keyword(s):  
Functional Characterization ◽  
Brain Networks ◽  
Three Dimensional ◽  
In Vitro Modeling ◽  
Cortical Cultures
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