Fig. 1. Overall structure of RtMprF(DDM)-nanodic homodimer at 3.7-Å resolution.

Cryo-EM densities of RtMprF dimer embedded in a nanodisc viewed along membrane plane (a) and along membrane normal from periplasmic side (b). Color codes: light green and light blue, two adjacent monomers of RtMprF dimer; yellow, lipid molecules; gray, nanodisc scaffold, uninterpreted lipid and other densities from adjacent RtMprF dimer. Cartoon models of RtMprF dimer viewed along membrane plane (c) and along membrane normal from periplasmic side (d). The four phospholipid molecules at the dimer interface are highlighted as sphere models and the LysPG inside monomers are shown as stick models. PG phosphatidylglycerol. e Western blot of the crosslinked products of RtMprF protein in the membrane. The asterisk indicates the position of RtMprF monomer, while the arrowhead labels the position of RtMprF dimer. DSS was used for the crosslinking experiment. The experiment was repeated independently three times with similar results. f The interfacial tubular void space at the dimer interface accommodating the four acyl chains from the PG molecules. The sectional view of the surface model of monomer A is shown and monomer B is omitted for clarity. PG molecules are shown as stick models.