Distance distributions for spin pairs that span the Ras-like and helical domains of Gαi1•GDP and the corresponding Gαi1:Ric-8A complex. (A) Distance distributions for the indicated pairs are shown for Gαi1•GDP (black traces) and for the complex with Ric-8A (red traces). Based on the DEER data collection time, upper limits for reliable distance and width determination are shown as cyan and magenta bars, respectively, on the distance axis. (B) CW EPR spectra for the corresponding doubly labeled proteins in the Gαi1•GDP (black), Gαi1:Ric-8A complex (red), and after the addition of GTPγS (green). The scan width in magnetic field is 100 G. Insets for 90R1/214R1 provide vertically expanded views of the low and high field regions in the GDP and Ric-8A-bound states to more clearly reveal features corresponding to immobilized states (arrows). For 147R1/235R1 broadening extending beyond 100 G reveals magnetic dipolar interaction in Gαi1•GDP but not in the complex with Ric-8A. Slight dipolar broadening is also seen in 90R1/238R1.