Dissociation of a native dimer to a molten globule monomer. Effects of pressure and dilution on the association equilibrium of arc repressor.

摘要: Abstract The monomer-dimer association reaction of Arc repressor was studied by pressure-induced dissociation and dilution. measured the decrease (red shift) in average energy emission tryptophan fluorescence. Pressure also promoted a excited-state lifetime single tryptophanyl residue, Trp14. These observations suggest that Trp14 becomes exposed to an aqueous environment following dissociation. pressure-dissociation curves were concentration dependent, with P 1 2 (half-dissociation pressure) shifting higher pressures as increased. constant (Kd0) obtained extrapolating atmospheric pressure similar determined from dilution curve (Kd0 = 30 n m ). An anomolous steepness response observed, suggesting conformational changes occur result repressor. Binding bis(8-anilinonaphthalene-1-sulfonate) not significantly affected dissociation, whereas thermal or urea denaturation accompanied dramatic binding. results follow induced are more limited than those denaturation. anisotropy decreased about one-half, globular dimer compact monomer. On other hand, increase anisotropy, expected for random-coil conformation. Dissociated has hydrodynamic properties folded dissociated high degree exposure hydrophobic side-chains, distribution conformations is much broader dimer. features subunit molten globule. interaction substantially increased amino acid substitution (Pro8 → Leu), free stabilization amounted −2·9 kcal/mol. This stability suggests residue 8 located interface part tertiary most quaternary structure constraints between intersubunit β-strands.