Co-operative binding of oxytocin to bovine neurophysin II.
The interaction of oxytocin with bovine neurophysin II in 0.1 M-sodium phosphate, pH 5.8, was investigated by equilibrium-dialysis and sedimentation studies. Sigmoidality of the binding curve is attributed to isomerization, either hormone-induced or pre-existing, with preferential binding of oxytocin to one isomeric state. Results are consistent with a binding equation of the form r = (2P[S]+2PQ[S]2)/(1+2P[S]+PQ[S]2) and values of 0.7 X 10(5)M-1 and 1.3 X 10(5)M-1 for P and Q respectively. The significance of these two parameters in relation to current theories of allostery is also discussed.
D000818:Animals; D002417:Cattle; D007700:Kinetics; D009481:Neurophysins / Q000378:metabolism*; D010121:Oxytocin / Q000378:metabolism*; D011485:Protein Binding
D009481:Neurophysins; D010121:Oxytocin