This entry describes the HQNO-bound alternative complex III from the anoxygenic phototrophic bacterium Chloroflexus aurantiacus for which the structure has been determined at 1.9 Å resolution (Xin et al. 2024). A more detailed description is presented in the family description and especially by this reference.  There are seven known subunites as follows: Subunits B, C, D, E, F, G, and I.  They are to be found in NCBI under the general ID # 8X2J_ followed by the number of the subunit as indicated above.  These subunits are:
B:  1029 aas and possibly 2 TMSs, 8X2J_B; FeS cluster-containing hydrogenase component-like protein
C:  486 aas and probably 10 TMSs, 8X2J_C: Polysulfide reductase, NrfD
D:  179 aas and 2 TMSs.
E:  205 aas and 1 N-terminal TMS
F:  411 aas and 10 TMSs. Subunits C and F are homologous, both with 10 TMSs, although they are distant in sequence.
G:  112 aas and 1 TMS
I:  37 aas and 1 TMS.