Article Abstract:
GalR mutants are defective in formation of repressosomes, DNA loops to which the name 'repressosome' has been applied. Transcription repression of the galactose operon of Escherichia coli must have the binding of the GalR repressor to tandem operators on either side of the promoters, negatively supercoiled DNA, and HU, the binding of histone-like protein, to a position between the GalR-binding sites. Protein-protein interactions mediate formation of a nucleoprotein complex, the repressosome. For analyzing structure of the repressosome, galR (ital) mutants with single amino acid substitutions in GalR bring defects in loop formation with the protein's operator-binding activity retained.
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Article Abstract:
Recruitment of HU, a prokaryotic histone-like protein, by piggyback is discussed with attention to a special role of GalR in repressosome assembly. The first example of HU in specific contact with another protein has been found in vitro and in vivo. In Gal repressosome assembly, a DNA loop is formed by the interaction of two GalR, bound to two distal operators, and the binding of HU to an architecturally critical position on DNA to helps along the GalR-GalR interaction.
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Article Abstract:
The Gal repressosome is a complicated high level nucleoprotein, which contains the record of the gal operon in Escherichia coli. Moreover, this method can be utilized to segregate between otherwise non-identifiable DNA trajectories in complicated nucleoprotein machines.
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