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#AraC protein

2 public questions tagged with this topic.

Gene regulation in Prokaryotes

In absence of arabinose, AraC binds to

Without L-arabinose, AraC apoprotein adopts conformation strongly promoting looping-mediated repression of araBAD operon. Dimer bridges high-affinity araO2 site centered approximately minus 280 upstream and araI1 site at minus 106, with intervening 210 base pairs bent into looped architecture demonstrated by electron microscopy. Crystallographic studies show N-terminal arms dimerize antiparallel, stabilizing loop topology. Looped conformation buries PBAD minus35 promoter element and occludes CAP-cAMP binding site, preventing RNA polymerase holoenzyme initiation. Approximately twenty AraC molec

Ref: Science DNA Looping by AraC – apo-AraC prefers looping between araO2 and araI1 repressing araBAD.

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Gene regulation in Prokaryotes

AraC protein functions as

AraC protein embodies remarkable dual regulatory function determined by arabinose-dependent conformational switch. Polypeptide of 292 residues contains N-terminal dimerization and arabinose-binding domain linked via flexible interdomain arm to C-terminal DNA-binding domain possessing two helix-turn-helix motifs. Apo form without arabinose favors interaction binding to distal O2 operator and I1 half-site forming DNA repression loop that blocks polymerase. Arabinose-bound form reorganizes N-terminal arm, neutralizes arm dimer interactions, shifts DNA-binding specificity to adjacent I1-I2 half-si

Ref: L-arabinose operon review – AraC is dual activator-repressor; apo-AraC loops araI1-O2 (210 bp) to repress.

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