TABLE 5

Allosteric parameters of affinity (pKB), binding cooperativity (logαNMS) of basic peptides, and [3H]NMS dissociation rate (koff) at the wild type

Values represent the mean ± S.E. from at least three experiments performed in duplicate.

WTN410K+T423K
pKBaLogαNMSbnckoff (min−1)dnpKBaLogαNMSbnkoff (min−1)cn
PLA6.32 ± 0.08−1.51 ± 0.2240.021 ± 0.002^35.76 ± 0.20*−0.19 ± 0.03*30.006 ± 0.0013
MBPn.a.n.a.4n.t.n.t.n.a.n.a.4n.t.n.t.
Protamine6.08 ± 0.09−1.08 ± 0.1030.014 ± 0.002^35.46 ± 0.12*−0.79 ± 0.15*50.006 ± 0.0013
  • n.a., not applicable, as no alteration of the specific binding of the radioligand was observed, and therefore, no estimate could be provided; n.t., not tested.

  • a Negative logarithm of the allosteric modulator equilibrium dissociation constant.

  • b Logarithm of the cooperativity factor for the interaction between the peptides and [3H]NMS.

  • c Number of experiments performed.

  • d Dissociation rate constant of the [3H]NMS in the presence of the indicated ligand (control values in the absence of ligand: WT koff = 0.043 ± 0.003 min−1, N410K+T423K koff = 0.007 ± 0.001 min−1).

  • * Significantly different from the corresponding value at the wild type (P < 0.05), Student’s t test.

  • ^ Significantly different from control koff (P < 0.05), one-way analysis of variance with Dunnett’s post-test.