Fig. 4: Crucial binding position of OcHeR for OmrDE.

a Binding affinities of OcHeR for OmrD^tcE^tc, OmrD, OmrE, and OmrDE from ITC analysis in Table 2 and Supplementary Figs. 12 and 13. The K_d values are estimated using a one site binding model. ITC analysis of OcHeR R233Q for OmrDE is evaluated using a sequential binding site model: R233Q-1, first binding; R233Q-2, second binding. Measurements were conducted in an independent experimental group (n = 2 to 5). Data are presented as mean value ± SEM. b, c Protein–protein docking simulation between modeled OcHeR homodimer based on PDB code: 6SU4 and modeled OmrDE heterodimer based on PDB code: 6RAF. OcHeR, OmrD, and OmrE structures are shown in pink, cyan, and yellow, respectively. b Residues at a distance of 5 Å from the interface between OcHeR and OmrDE are shown. c OcHeR homodimer is expressed in two subunits (monomer). The distance (2.0–2.2 Å) between the hydrogen bonds of the interacting residues of OcHeR and OmrDE was determined using the polar interaction tool; it is indicated by yellow dotted lines and marked by yellow arrows. The positions of residues in OcHeR and OmrDE are indicated in pink and black text, respectively. d Scheme of the crystal structure of OcHeR is shown from the top angle, with each subunit of OcHeR separated by dotted lines. Each mutation position is indicated by text with non-binding and fold-changes of the K_d values of OcHeR mutants for OmrDE compared with that of OcHeR WT for OmrDE. ICL intracellular loop, ND not detected, NB non-binding.