TABLE 6

Affinity (pKB) and functional cooperativity with ACh (logαβACh) estimates of the basic peptides, PLA, protamine, and MBP

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

WTN410K+T423K
pKBaLogαβAChbncpKBLogαβAChn
PLA7.00 ± 0.05−3#36.41 ± 0.25*−0.70 ± 0.56*3
MBP6.54 ± 0.29−3#4n.a.n.a.4
Protamine6.01 ± 0.25−0.86 ± 0.194n.a.n.a.4
  • n.a., not applicable, as no alteration of the EC50 of ACh was observed, and therefore, no estimate could be provided.

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

  • b Logarithm of the cooperativity factor for the interaction between the peptides and ACh.

  • c Number of experiments performed.

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

  • # Interaction was indistinguishable from competition (F-test), indicative of very high negative cooperativity (αβ → 0), and thus the cooperativity factor was constrained to an arbitrarily low value.