9.B.393.  The DUF2231 (DUF2231) Family 

These proteins are of about 150 to 200 aas in size and have 4 TMSs.  Some homologues are annotated as Rieske 2Fe-2S proteins, and others are annotated as rubrerythrin or rubredoxin-type Fe(cys)4 proteins.  Consequently, they may be redox proteins.