scholarly journals Characterization of two mutant lactose repressor proteins containing single tryptophans.

1990 ◽  
Vol 265 (34) ◽  
pp. 21061-21067
Author(s):  
J A Gardner ◽  
K S Matthews
Keyword(s):  
Lactose Repressor ◽  
Repressor Proteins

scholarly journals Identification and Characterization of a Gene Cluster for Synthesis of the Polyketide Antibiotic 2,4-Diacetylphloroglucinol from Pseudomonas fluorescens Q2-87

1999 ◽  
Vol 181 (10) ◽  
pp. 3155-3163 ◽  
Author(s):  
M. Gita Bangera ◽  
Linda S. Thomashow
Keyword(s):  
Genomic Dna ◽  
Plant Pathogens ◽  
Polyketide Synthase ◽  
Open Reading Frames ◽  
Fungal Plant Pathogens ◽  
Repressor Proteins ◽  
Flanking Regions ◽  
Identification And Characterization ◽  
Reading Frames

The polyketide metabolite 2,4-diacetylphloroglucinol (2,4-DAPG) is produced by many strains of fluorescent Pseudomonas spp. with biocontrol activity against soilborne fungal plant pathogens. Genes required for 2,4-DAPG synthesis by P. fluorescensQ2-87 are encoded by a 6.5-kb fragment of genomic DNA that can transfer production of 2,4-DAPG to 2,4-DAPG-nonproducing recipientPseudomonas strains. In this study the nucleotide sequence was determined for the 6.5-kb fragment and flanking regions of genomic DNA from strain Q2-87. Six open reading frames were identified, four of which (phlACBD) comprise an operon that includes a set of three genes (phlACB) conserved between eubacteria and archaebacteria and a gene (phlD) encoding a polyketide synthase with homology to chalcone and stilbene synthases from plants. The biosynthetic operon is flanked on either side by phlEand phlF, which code respectively for putative efflux and regulatory (repressor) proteins. Expression in Escherichia coli of phlA, phlC, phlB, andphlD, individually or in combination, identified a novel polyketide biosynthetic pathway in which PhlD is responsible for the production of monoacetylphloroglucinol (MAPG). PhlA, PhlC, and PhlB are necessary to convert MAPG to 2,4-DAPG, and they also may function in the synthesis of MAPG.

scholarly journals Characterization of the folding landscape of monomeric lactose repressor: Quantitative comparison of theory and experiment

2005 ◽  
Vol 102 (41) ◽  
pp. 14569-14574 ◽  
Author(s):  
P. Das ◽  
C. J. Wilson ◽  
G. Fossati ◽  
P. Wittung-Stafshede ◽  
K. S. Matthews ◽  
...  
Keyword(s):  
Quantitative Comparison ◽  
Lactose Repressor ◽  
Theory And Experiment

scholarly journals Cloning and Characterization of a Tetracycline Resistance Determinant Present in Agrobacterium tumefaciens C58

1999 ◽  
Vol 181 (2) ◽  
pp. 618-626 ◽  
Author(s):  
Zhao-Qing Luo ◽  
Stephen K. Farrand
Keyword(s):  
Agrobacterium Tumefaciens ◽  
Promoter Region ◽  
Tetracycline Resistance ◽  
Homologous Region ◽  
Polycyclic Compounds ◽  
Repressor Proteins ◽  
Repressive Effect ◽  
Agrobacterium Tumefaciens C58 ◽  
Spontaneous Mutants

ABSTRACT Agrobacterium tumefaciens C58 and its derivatives give rise to spontaneous mutants resistant to tetracycline at a high frequency. We observed that a mutation affecting a tRNA processing function significantly affected the emergence of such mutants, suggesting that C58 contained a positively acting gene conferring resistance to tetracycline. A cosmid clone conferring resistance to tetracycline in Escherichia coli andAgrobacterium was isolated from a genomic bank of one such mutant. Subcloning, transposon mutagenesis, and DNA sequence analysis revealed that this DNA fragment contained two divergently transcribed genes, tetA and tetR, encoding products that were very similar to proteins of the Tet(A) class of tetracycline resistance systems. In the clone from this mutant, tetR was disrupted by an IS426. The homologous region from wild-type NT1 contained an intact tetR gene and did not confer resistance to tetracycline. Hybridization analysis showed that of 22 members of the genus Agrobacterium surveyed, only strains C58 and T37 contained the tet determinant. Moreover, only these two strains mutated to resistance to this antibiotic. Unlike other Tet(A) systems, neither tetracycline nor a series of its derivatives induced the expression of this tet gene unit. Other polycyclic compounds, including many of plant origin, also did not induce this tet gene system. The divergent promoter region of this tet system contained a single inverted repeat element identical to one such operator repeat in the promoter region of the tet determinant from the IncP1α R plasmid RP4. TetR repressor proteins from the Agrobacterium tetsystem and from RP4 interacted with the heterologous operators. While the repressive effect of the TetR protein from strain C58 (TetRC58) on the tetA gene from strain RP4 (tetA RP4) was not relieved by tetracycline, repression of tetA C58 by TetRRP4was lifted by this antibiotic.

scholarly journals Complete Nucleotide Sequence of the LE1 Prophage from the Spirochete Leptospira biflexa and Characterization of Its Replication and Partition Functions

2005 ◽  
Vol 187 (12) ◽  
pp. 3931-3940 ◽  
Author(s):  
Pascale Bourhy ◽  
Lionel Frangeul ◽  
Elisabeth Couvé ◽  
Philippe Glaser ◽  
Isabelle Saint Girons ◽  
...  
Keyword(s):  
Genetic Manipulation ◽  
Plasmid Stability ◽  
Shuttle Vector ◽  
Gc Content ◽  
Open Reading Frames ◽  
Partition Functions ◽  
Shuttle Vectors ◽  
Repressor Proteins ◽  
Replication Region

ABSTRACT The first and, to date, only extrachromosomal circular replicon identified in the spirochete Leptospira is the LE1 prophage from Leptospira biflexa. The 74-kb LE1 genome has a GC content of 36%, which is similar to the GC content of Leptospira spp. Most of the 79 predicted open reading frames (ORFs) showed no similarities to known ORFs. However 21 ORFs appeared to be organized in clusters that could code for head and tail structural proteins and immunity repressor proteins. In addition, the pattern of gene expression showed that several LE1 genes are expressed specifically either in LE1 prophage or in L. biflexa late after infection. Since the LE1 prophage replicates autonomously as a circular replicon in L. biflexa, we were able to engineer an L. biflexa-Escherichia coli shuttle vector from a 5.3-kb DNA fragment of LE1 (Saint Girons et al., J. Bacteriol. 182:5700-5705, 2000), opening this genus to genetic manipulation. In this study, base compositional asymmetry confirms the location of the LE1 replication region and suggests that LE1 replicates via a bidirectional Θ-like replication mechanism from this unique origin. By subcloning experiments, the replication region can be narrowed down to a 1-kb region. This minimal replication region consists of a rep encoding a protein of 180 amino acids. Upstream from rep, putative partitioning genes, called parA and parB, were found to be similar to the par loci in Borrelia plasmids. A significant increase of plasmid stability in L. biflexa can be seen only when both parA and parB are present. These results enable the construction of new shuttle vectors for studying the genetics of Leptospira spp. This study will also contribute to a better knowledge of phages unrelated to lambdoid phages.

scholarly journals RGA & GAI: On the characterization of two DELLA plant growth repressor proteins

2018 ◽  
Vol 11 ◽  
Author(s):  
Daniela C Vaz ◽  
Raquel Sousa ◽  
Marco Simoes ◽  
Americo Rodrigues
Keyword(s):  
Plant Growth ◽  
Repressor Proteins

Morphological Characterization of Mycobacteriophage R1

1974 ◽  
Vol 32 ◽  
pp. 254-255
Author(s):  
B. L. Soloff ◽  
T. A. Rado
Keyword(s):  
Carbon Source ◽  
Stationary Phase ◽  
Growth Phase ◽  
Minimal Medium ◽  
Morphological Characterization ◽  
Logarithmic Growth Phase ◽  
Complete Lysis ◽  
Lysogenic Culture ◽  
Logarithmic Growth

Mycobacteriophage R1 was originally isolated from a lysogenic culture of M. butyricum. The virus was propagated on a leucine-requiring derivative of M. smegmatis, 607 leu−, isolated by nitrosoguanidine mutagenesis of typestrain ATCC 607. Growth was accomplished in a minimal medium containing glycerol and glucose as carbon source and enriched by the addition of 80 μg/ ml L-leucine. Bacteria in early logarithmic growth phase were infected with virus at a multiplicity of 5, and incubated with aeration for 8 hours. The partially lysed suspension was diluted 1:10 in growth medium and incubated for a further 8 hours. This permitted stationary phase cells to re-enter logarithmic growth and resulted in complete lysis of the culture.

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