8.A.112.2.1
The mitochondrial respiratory supercomplex factor 2 (Rcf2) of 224 aas and 4 apparent TMSs in a 2 + 2 TMS apparent arrangement.  According to Zhou et al. 2018, there is a 5th TMS at the C-terminus, but it is strongly hydrophilic.  See family description for the structure and function of Rcf2. Each Rcf2 monomer in the dimer has two soluble α-helices and five putative transmembrane (TM) α-helices, including an unexpectedly charged TMS at the C terminus, which mediates dimer formation. Inter-monomer salt bridges and hydrogen bondsare poresent at the dimer interface, which stabilize the Rcf2 dimer structure. Possible structural changes upon embedding Rcf2 into a native lipid environment have been proposed (Zhou et al. 2021).