Abstract
Abstract
The enzyme HydE is involved in the assembly of the [2Fe]
H
‐subcluster of the [FeFe]‐hydrogenase active site (also termed H‐cluster). The protein belongs to the radical SAM enzyme superfamily and uses a (κ
3
‐cysteinate‐Fe
II
(CN)(CO)
2
organometallic complex as substrate. Upon SAM cleavage, the 5′‐deoxyadenosyl radical attacks the cysteinate sulfur atom and produces two successive EPR active intermediates. Yet, the final product of the reaction remains unknown. In addition to the radical SAM [4Fe–4S]‐cluster, HydE from
Thermotoga maritima
exhibits an auxiliary [4Fe–4S]‐cluster located at the surface of the protein. This peculiarity allowed structural characterizations of FeS‐cluster assembly and degradation intermediate structures.