Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P51532 (transcriptional activator)
 6,546 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We describe a method to determine the magnitude of protein-induced DNA bends relative to a set of standard A tract bends using comparative gel electrophoresis. The DNA bend of interest was that induced by the catabolite activator protein (CAP), the transcriptional activator protein of the lac operon. The set of comparison molecules contained both bends of known magnitude and a bound CAP. The electrophoretic influence of the bound protein was accounted for by placing its binding site at the end of the molecule where its induced bend has little influence. Standard bends at the DNA center were introduced by incorporating 3-9 A6 tracts at approximately 10.5 base-pair phasing. The mobility of these control molecules was compared to the mobility of a test molecule of comparable length containing a central CAP-induced DNA bend. The CAP bend angle was found to be 5.6 +/- 0.3 A tract equivalents, or approximately 100 degrees, independent of the concentration of the gel used within the range tested. The dependence of gel retardation on DNA end-to-end distance was found to break down for A tract bend angles above 120 degrees, corresponding roughly to the angle beyond which the long axis of the molecule is no longer parallel to the end-to-end vector. We speculate that this may reflect a switch in the mode of migration of molecules through the gel.
Biopolymers 1990 Jan
PMID:Comparative gel electrophoresis measurement of the DNA bend angle induced by the catabolite activator protein. 215 60

The question of long-range allosteric transitions of DNA secondary structure and their possible involvement in transcriptional activation is discussed in the light of new results. A variety of recent evidence strongly supports a fluctuating long-range description of DNA secondary structure. Balanced equilibria between two or more different secondary structures, and the occurrence of very large domain sizes, have been documented in several instances. Long-range allosteric effects stemming from changes in sequence or secondary structure over a small region of the DNA have been observed to extend over distances up to hundreds of base pairs in some cases. The discovery that coherent bending strain beyond a threshold level in small (N < or = 250 base pairs (bp)] circular DNAs significantly alters the DNA secondary structure has important implications, especially for transcriptional activators that either bend the DNA directly or are involved in the formation of DNA loops of sufficiently small size (N < or = 250 bp). Whether the RNA polymerase is activated primarily via protein: protein contacts, as is widely believed, or instead via a bend-induced allosteric transition of the DNA in such a small loop, is now an open question. Binding of the transcriptional activator Sp1 to linear DNA induces a remarkably long-range change in its secondary structure, and catabolite activator protein binding to a supercoiled DNA behaves similarly, though possibly for different reasons. Compelling evidence for a bend-induced long-range structural transmission effect of the transcriptional activator integration host factor on RNA polymerase activity was recently reported. These results may augur a new paradigm in which allosteric transitions of duplex DNA, as well as of the proteins, are involved in the regulation of transcription.
Biopolymers 1997
PMID:The question of long-range allosteric transitions in DNA. 959 80

The transacting transcriptional activator (Tat) is a viral protein essential for activation of the human immunodeficiency virus (HIV) genes, and it plays an important role in HIV induced immunodeficiency. We report the NMR structural characterization of the active Tat Mal variant that belongs to a highly virulent D-subtype HIV type-1 (HIV-1) strain (Mal) found mainly in Africa. A full Tat Mal protein (87 residues) is synthesized. This synthetic protein is active in a transactivation assay with HeLa cells infected with the HIV long terminal repeated noncoding sequences of the HIV-1 provirus (LTR) lac Z gene. Homonuclear (1)H-NMR spectra allows the sequential assignment of the Tat Mal spin systems. Simulating annealing generates 20 conformers with similar folding. The geometry of the mean structure is optimized with energy minimization to obtain a final structure. As the European variant (Tat Bru) the N-terminal region of Tat Mal constitutes the core, and there is a hydrophobic pocket composed of the conserved Trp 11 interacting with several aromatic residues. The two functional regions of Tat (basic and the cysteine-rich regions) are well exposed to the solvent. A short alpha-helix is observed in region V adjacent to the basic region. This alpha helix induces local structural variations compared to the NMR structure of Tat Bru, and it brings the cysteine-rich and basic regions closer. This study suggests that similar folding exists among Tat variants.
Biopolymers 2001
PMID:Homonuclear (1)H-NMR assignment and structural characterization of human immunodeficiency virus type 1 Tat Mal protein. 1185 71

Polymeric micelles self-assembled from cholesterol-conjugated poly(ethylene glycol) (PEG) and anchored with transcriptional activator TAT peptide (TAT-PEG-b-Col) were fabricated for delivery of antibiotics across the blood-brain barrier (BBB). Ciprofloxacin, which demonstrated a high bactericidal effect, was efficiently loaded into the micelles by a membrane dialysis method. The ciprofloxacin-loaded micelles were characterized via dynamic light scattering and SEM. The micelles were spherical in nature, having an average diameter of smaller than 180 nm. Sustained release of ciprofloxacin was achieved over 6 h in phosphate-buffered saline (pH 7.4) at 37 degrees C. Confocal laser scanning microscopy reveals that the uptake of Fluorescein 5-isothiocyanate (FITC)-loaded TAT-PEG-b-Col micelles by human astrocytes was much higher than that of free FITC. Animal studies proved that these micelles crossed the BBB and entered the brain. The TAT-conjugated micelles may be used to deliver antibiotics across the BBB for treatment of brain infections.
Biopolymers 2008
PMID:Polymeric micelles anchored with TAT for delivery of antibiotics across the blood-brain barrier. 1841 28

Protein-protein interactions (PPIs) are essential for implementing cellular processes and thus methods for the discovery and study of PPIs are highly desirable. An emerging method for capturing PPIs in their native cellular environment is in vivo covalent chemical capture, a method that uses nonsense suppression to site specifically incorporate photoactivable unnatural amino acids (UAAs) in living cells. However, in one study we found that this method did not capture a PPI for which there was abundant functional evidence, a complex formed between the transcriptional activator Gal4 and its repressor protein Gal80. Here we describe the factors that influence the success of covalent chemical capture and show that the innate reactivity of the two UAAs utilized, (p-benzoylphenylalanine (pBpa) and p-azidophenylalanine (pAzpa)), plays a profound role in the capture of Gal80 by Gal4. Based upon these data, guidelines are outlined for the successful use of in vivo photo-crosslinking to capture novel PPIs and to characterize the interfaces.
Biopolymers 2014 Apr
PMID:Sequence context and crosslinking mechanism affect the efficiency of in vivo capture of a protein-protein interaction. 2403 47