Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.1.2.42 (DTA)
 1,693 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The bacteriophage T3 promoter can be selectively transcribed by the corresponding RNA polymerase in eukaryotic cells. A toxic gene can in principle be linked to this promoter in a "dormant" and innocuous transgene in a transgenic animal. In this scheme, the activating strain expresses the RNA polymerase. When expression of the gene is needed in the progeny, the 2 lines are crossed. However, when a single molecule is sufficient to kill the cell--as with the diphtheria toxin--transcriptional "leakage" from the promoter may not be tolerated by the cell, even when extremely weak. Therefore, prior to more elaborate studies, diphtheria toxin, as a prototype of a gene toxic to the organism, has been linked to the bacteriophage T3 promoter in a T3-E-DTA construct. The T3-E-DTA plasmid has been transiently transfected into human embryonic kidney derived cells together with a lacZ plasmid. By co-transfection, the T3-E-DTA cells can be readily identified as lacZ positive, and their fate followed by the production of beta-galactosidase at the single cell or overall population level. In spite of the extreme toxicity of the toxin, the cells tolerate the presence of the T3-E-DTA construct, and are only killed--with a high efficiency--when the T3 RNA polymerase is present. Transactivation is usually restricted to the auxiliary factors of transcription. With this study, the promoter and the polymerase are revealed as potential and efficient inducible and activating elements of a very simple binary system.
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PMID:A bacteriophage T3 promoter can be linked to a lethal gene without detectable toxicity for eukaryotic cells. Interest for inducible transgenes. 909 Nov 77

The Escherichia coli iron transport system via ferrichrome belongs to the group of ATP-dependent transporters that are widely distributed in prokaryotes and eukaryotes. Transport across the cytoplasmic membrane is mediated by three proteins: FhuD in the periplasm, FhuB in the cytoplasmic membrane and FhuC (ATPase) associated with the inside of the cytoplasmic membrane. Interaction of FhuD with FhuB was studied in vitro with biotinylated synthetic 10 residue and 20-24 residue peptides of FhuB by determining the activity of beta-galactosidase linked to the peptides via streptavidin. Peptides identical in sequence to only one of the four periplasmic loops (loop 2), predicted by a transmembrane model of FhuB, and peptides representing a transmembrane segment and part of the adjacent cytoplasmic loop 7 of FhuB bound to FhuD. Decapeptides were transferred into the periplasm of cells through a FhuA deletion derivative that forms permanently open channels three times as large as the porins in the outer membrane. FhuB peptides that bound to FhuD inhibited ferrichrome transport, while peptides that did not bind to FhuD did not affect transport. These data led us to propose that the periplasmic FhuD interacts with a transmembrane region and the cytoplasmic segment 7 of FhuB. The transmembrane region may be part of a pore through which a portion of FhuD inserts into the cytoplasmic membrane during transport. The cytoplasmic segment 7 of FhuB contains the conserved amino acid sequence EAA...G (in FhuB DTA ...G) found in ABC transporters, which is predicted to interact with the cytoplasmic FhuC ATPase. Triggering of ATP hydrolysis by substrate-loaded FhuD may occur by physical interaction between FhuD and FhuC, which bind close to each other on loop 7. Although FhuB consists of two homologous halves, FhuB(N) and FhuB(C), the sites identified for FhuD-mediated ferrichrome transport are asymmetrically arranged.
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PMID:ATP-dependent ferric hydroxamate transport system in Escherichia coli: periplasmic FhuD interacts with a periplasmic and with a transmembrane/cytoplasmic region of the integral membrane protein FhuB, as revealed by competitive peptide mapping. 942 46