3.D.12.1.1
The FixABCX electron flow complex where FixA and FixB are soluble proteins of 283 and 365 aas, respectively, while FixC is a membrane protein of 433 aas and 1 - 8 TMSs (see family description), and FixX is a ferridoxin-like protein of 96 aas. FixC shows limited similarity to proteins in TC families 3.A.10 and 3.D.7, and FixX shows similarity to proteins in families 3.D.6, 7 and 8 as well as 5.A.3. Homologues of FixC are annotated as (1) N₂ fixation protein, FixC, (2) FAD-dependent monooxygenase, (3) FAD-binding protein, and (4) electron transfer flavoprotein quinone oxidoreductase.