3-AP– and pH-induced conformational changes in loop F of the ELIC-GLIC chimera. (A) Locations of examined residues in ELIC-GLIC (left) and spin-normalized CW-EPR spectra of the residues in the apo state, with 20 mM 3-AP, and at pH 3.0 (right). (B) The corresponding distances mapped on the ELIC structure (PDB accession no. 3RQU; left). The DEER echo and the distance distribution under the three conditions (right). The peak values for distance distribution are marked for the apo state. The arrows highlight the direction of change (orange, 3-AP; green, pH 3.0).