Equilibrium dissociation and unfolding of the Arc repressor dimer.
The equilibrium unfolding reaction of Arc repressor, a dimeric DNA binding protein encoded by bacteriophage P22, can be monitored by fluorescence or circular dichroism changes. The stability of Arc is concentration dependent, and the unfolding reaction is well described as a two-state transition from folded dimer to unfolded monomer. The stability of the protein is decreased at low pH and increased by high salt concentration. The salt dependence suggests that two ions bind preferentially to the folded protein. In 10 mM potassium phosphate (pH 7.3) and 100 mM KCl, the unfolding free energy reaches a maximum near room temperature. The results suggest that at the low protein concentrations where operator DNA binding is normally measured, Arc is predominantly monomeric and unfolded.
Bowie
J U
JU
Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
Sauer
R T
RT
D002942:Circular Dichroism; D004268:DNA-Binding Proteins / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D011189:Potassium Chloride / Q000494:pharmacology; D011487:Protein Conformation; D011489:Protein Denaturation; D012097:Repressor Proteins / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013696:Temperature; D013816:Thermodynamics; D014157:Transcription Factors / Q000378:metabolism; D014764:Viral Proteins / Q000378:metabolism; D054334:Viral Regulatory and Accessory Proteins
D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins; D011189:Potassium Chloride