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9.B.361.  The Small 4 TMS Protein (S4P) Family 

Most of the proteins of this family are of about 130 - 180 aas with 4 TMSs in a 3 + 1 TMS arrangement.  However, some have only two TMSs corresponding to TMSs 1 & 2 or 3 & 4 of the 4 TMS proteins.  5 TMS homologues are also present in the family. Some members of this family have been annotated as 'hydrogenase'.