Cooperation of the helicase core(s) with the RBD(s): conformational changes of the helicase core. (A) Single-molecule FRET histograms for donor/acceptor-labeled Hera_E115C_E227C (black; same data as in Fig. 3A), Hera_E115C_E227C/Hera_208–419 (cis-heterodimer: one core, one RBD in cis; green), Hera_1–419_E115C_E227C/Hera_370–510 (trans-heterodimer: one core, one RBD in trans; cyan), Hera_E115C_E227C/Hera_1–419_K51Q (cis-like heterodimer: two cores, one functional core, RBD in cis to the functional core; dark green), and Hera_K51Q/Hera_1–419_E115C_E227C (trans-like heterodimer: two cores, one functional core, RBD in trans to the functional core; dark blue) in the absence (lines, no fill) and presence of 5 mM ADPNP and 4.8 μM of 32mer RNA (lines, colored fill). Representative histograms from at least two independent experiments. (B) FRET efficiency as a function of the 32mer concentration for donor/acceptor-labeled Hera_E115C_E227C (black; same data as in Fig. 3B), Hera_E115C_E227C/Hera_208–419 (cis-heterodimer; green), Hera_1–419_E115C_E227C/Hera_370–510 (trans-heterodimer; cyan), Hera_E115C_E227C/Hera_1–419_K51Q (cis-like heterodimer; dark green), and Hera_K51Q/Hera_1–419_E115C_E227C (trans-like heterodimer; dark blue) in the absence and presence of 5 mM ADPNP. Error bars are errors of the mean from at least two independent experiments.