| B | NADH_4Fe-4S | e6ttlB3 | A: alpha bundles | X: Bromodomain-like | H: Nqo1C-terminal domain-like (From Topology) | T: Nqo1C-terminal domain-like | F: NADH_4Fe-4S | ECOD (1.6) |
| B | Fe_hyd_lg_C | e6ttlB1 | A: a/b three-layered sandwiches | X: Fe-only hydrogenase (From Topology) | H: Fe-only hydrogenase (From Topology) | T: Fe-only hydrogenase | F: Fe_hyd_lg_C | ECOD (1.6) |
| B | Fe_hyd_SSU | e6ttlB2 | A: extended segments | X: Fe-only hydrogenase smaller subunit (From Topology) | H: Fe-only hydrogenase smaller subunit (From Topology) | T: Fe-only hydrogenase smaller subunit | F: Fe_hyd_SSU | ECOD (1.6) |
| A | NADH_4Fe-4S | e6ttlA3 | A: alpha bundles | X: Bromodomain-like | H: Nqo1C-terminal domain-like (From Topology) | T: Nqo1C-terminal domain-like | F: NADH_4Fe-4S | ECOD (1.6) |
| A | Fe_hyd_lg_C | e6ttlA1 | A: a/b three-layered sandwiches | X: Fe-only hydrogenase (From Topology) | H: Fe-only hydrogenase (From Topology) | T: Fe-only hydrogenase | F: Fe_hyd_lg_C | ECOD (1.6) |
| A | Fe_hyd_SSU | e6ttlA2 | A: extended segments | X: Fe-only hydrogenase smaller subunit (From Topology) | H: Fe-only hydrogenase smaller subunit (From Topology) | T: Fe-only hydrogenase smaller subunit | F: Fe_hyd_SSU | ECOD (1.6) |