Table 1.

Summary of I-actin: MV FlAsH energy transfer results

Nucleotide statesR0, Å*Steady state
Lifetime
FRET efficiencyr, Å(rminrmax)§FRET efficiencyr, Å(rminrmax)§
MV E442A FlAsH: I-actin (Rigor)510.23 ± 0.0262.4 ± 1.2(43.4–81.9)0.36 ± 0.0556.1 ± 2.2(40.0–73.7)
MV E442A FlAsH: I-actin (ATP)510.16 ± 0.0167.2 ± 0.6(46.3–88.3)0.24 ± 0.0561.8 ± 3.1(42.6–81.2)
  • *Förster distance at which the efficiency of energy transfer is 50%.

  • Steady-state FRET efficiency calculated from the titration curve with I-actin in the presence of ATP (errors represent standard error of the fit). In the rigor state errors represent standard deviation of the mean FRET efficiency.

  • Distance (r) between the donor and acceptor probes calculated by using a κ2 value of 2/3.

  • §The range of distances (rminrmax) possible based on the maximum and minimum value for κ2 determined from the steady-state and limiting anisotropy (20, 21).

  • FRET efficiency calculated from the decrease in donor lifetime (E = 1 − τ DAD). The average lifetime 〈τ〉 of the donor was determined in the presence and absence of acceptor. The errors represent the standard deviation of the mean from 3 to 4 separate experiments that included different protein preparations.