TABLE 1

Inhibitory parameters (IC50, maximal inhibition, and inhibitory efficiency) of blebbistatin, NBleb, and AmBleb for seven different myosin-2 isoforms

SubstanceIC50 (μM)a
NM2ANM2BNM2CSkeletalCardiacSmoothDicty
Blebbistatin13 ± 415 ± 53.5 ± 0.80.27 ± 0.072.5 ± 0.44.1 ± 1.06.4 ± 2.0
NBleb18 ± 414 ± 25.1 ± 2.90.072 ± 0.0233.9 ± 0.25.6 ± 0.59.0 ± 1.2
AmBleb9.5 ± 3.721 ± 87.2 ± 0.70.98 ± 0.155.3 ± 0.613 ± 28.5 ± 1.7
Maximal inhibition (%)a
NM2ANM2BNM2CSkeletalCardiacSmoothDicty
Blebbistatin10095 ± 1298 ± 698 ± 194 ± 490 ± 5100
NBleb10086 ± 697 ± 399 ± 196 ± 299 ± 3100
AmBleb60 ± 878 ± 1210099 ± 292 ± 3100100
Inhibitory efficiency (%/μM)b
SkeletalCardiacSkeletal/cardiac ratio
blebbistatin363389.7
NBleb13752556
AmBleb101435.8
  • a IC50 and maximal inhibition values were determined from hyperbolic fits (Fig. 1). Data represent the average ± S.D. (n = 3–12). Fits were constrained to have maximal inhibition between 0% and 100%, so S.E. of the fit is not shown when this constraint was hit.

  • b Inhibitory efficiency is defined as (kinh = Imax/IC50), i.e., maximal inhibition divided by IC50 from hyperbolic fits in Fig. 1.