[FeFe] hydrogenases carry out the redox interconversion of protons and molecular hydrogen (2H⁺ + 2e⁻ ⇌ H₂) at a complex Fe–S active site known as the H-cluster. The H-cluster consists of a [4Fe–4S] subcluster, denoted here as [4Fe]_H, linked via a cysteine sulfur to an interesting organometallic [2Fe]_H subcluster thought to be the subsite where the catalysis occurs. This [2Fe]_H subcluster consists of two Fe atoms, linked with a bridging CO and a bridging SCH₂NHCH₂S azadithiolate (adt), with additional terminal CO and CN ligands bound to each Fe. Synthesizing such a complex organometallic unit is a fascinating problem in biochemistry, complicated by the toxic nature of both the CO and CN⁻ species and the relative fragility of the azadithiolate bridge. It has been known for a number of years that this complex biosynthesis is carried out by a set of three essential Fe–S proteins, HydE, HydF, and HydG. HydF is a GTPase, while HydE and HydG are both members of the large family of radical S-adenosylmethionine (rSAM) enzymes. In this perspective we describe the history of research and discovery concerning these three Fe–S “maturase” proteins and describe recent evidence for a sequential biosynthetic pathway beginning with the synthesis of a mononuclear organometallic [Fe(II)(CO)₂CN(cysteine)] complex by the rSAM enzyme HydG and its subsequent activation by the second rSAM enzyme HydE to form a highly reactive Fe(I)(CO)₂(CN)S species. In our model a pair of these Fe(I)(CO)₂(CN)S units condense to form the [Fe(CO)₂(CN)S]₂ diamond core of the [2Fe]_H cluster, requiring only the installation of the central CH₂NHCH₂ portion of the azadithiolate bridge, whose atoms are all sourced from the amino acid serine. This final step likely occurs with an interplay of HydE and HydF, the details of which yet remain to be elucidated.

中文翻译：

---

[FeFe]氢化酶催化 H 簇的生物合成：Fe-S 成熟酶蛋白 HydE、HydF 和 HydG 的作用

[FeFe]氢化酶在称为 H 团簇的复杂 Fe-S 活性位点上进行质子和分子氢 (2H ⁺ + 2e ⁻ ⇌ H _{2 ) 的氧化还原相互转化。}H 簇由 [4Fe–4S] 子簇组成，此处表示为 [4Fe] _H，通过半胱氨酸硫连接到一个有趣的有机金属 [2Fe] _H子簇，该子簇被认为是发生催化的子位点。该 [2Fe] _H子簇由两个 Fe 原子组成，与桥接 CO 和桥接 SCH ₂ NHCH ₂ S 氮杂二硫醇盐 (adt) 连接，另外的末端 CO 和 CN 配体与每个 Fe 结合。^{合成这样一个复杂的有机金属单元是生物化学中一个令人着迷的问题，由于 CO 和 CN -}物质的毒性以及氮杂二硫醇桥的相对脆弱性而变得复杂。多年来人们已经知道这种复杂的生物合成是由一组三种必需的 Fe-S 蛋白 HydE、HydF 和 HydG 进行的。HydF 是一种 GTP 酶，而 HydE 和 HydG 都是自由基S-腺苷甲硫氨酸 (rSAM) 酶大家族的成员。从这个角度来看，我们描述了有关这三种 Fe-S“成熟酶”蛋白的研究和发现的历史，并描述了从单核有机金属 [Fe( II )(CO) ₂ CN(半胱氨酸)的合成开始的连续生物合成途径的最新证据。)] 复合物由 rSAM 酶 HydG 形成，随后由第二个 rSAM 酶 HydE 激活，形成高反应性 Fe( I )(CO) ₂ (CN)S 物质。在我们的模型中，一对这样的 Fe( I )(CO) ₂ (CN)S 单元凝结形成[2Fe] _{H簇的 [Fe(CO) 2} (CN)S] ₂金刚石核心，仅需要安装氮杂二硫醇桥的中心CH ₂ NHCH ₂部分，其原子全部源自氨基酸丝氨酸。这最后一步可能是在 HydE 和 HydF 相互作用的情况下发生的，其细节仍有待阐明。