Hartmann Sven, Frielingsdorf Stefan, Ciaccafava Alexandre, Lorent Christian, Fritsch Johannes, Siebert Elisabeth, Priebe Jacqueline, Haumann Michael, Zebger Ingo, Lenz Oliver
Department of Chemistry, Sekr. PC14 , Technische Universität Berlin , 10623 Berlin , Germany.
Department of Biology , Humboldt-Universität zu Berlin , 10115 Berlin , Germany.
Biochemistry. 2018 Sep 11;57(36):5339-5349. doi: 10.1021/acs.biochem.8b00760. Epub 2018 Aug 24.
The catalytic properties of hydrogenases are nature's answer to the seemingly simple reaction H ⇌ 2H + 2e. Members of the phylogenetically diverse subgroup of [NiFe] hydrogenases generally consist of at least two subunits, where the large subunit harbors the H-activating [NiFe] site and the small subunit contains iron-sulfur clusters mediating e transfer. Typically, [NiFe] hydrogenases are susceptible to inhibition by O. Here, we conducted system minimization by isolating and analyzing the large subunit of one of the rare members of the group of O-tolerant [NiFe] hydrogenases, namely the preHoxG protein of the membrane-bound hydrogenase from Ralstonia eutropha. Unlike previous assumptions, preHoxG was able to activate H as it clearly performed catalytic hydrogen/deuterium exchange. However, it did not execute the entire catalytic cycle described for [NiFe] hydrogenases. Remarkably, H activation was performed by preHoxG even in the presence of O, although the unique [4Fe-3S] cluster located in the small subunit and described to be crucial for tolerance toward O was absent. These findings challenge the current understanding of O tolerance of [NiFe] hydrogenases. The applicability of this minimal hydrogenase in basic and applied research is discussed.
氢化酶的催化特性是自然界对看似简单的反应H⇌2H⁺ + 2e的解答。[NiFe]氢化酶在系统发育上具有多样性，其成员通常至少由两个亚基组成，其中大亚基含有激活H的[NiFe]位点，小亚基含有介导电子转移的铁硫簇。通常，[NiFe]氢化酶易受O的抑制。在此，我们通过分离和分析耐O的[NiFe]氢化酶组中罕见成员之一的大亚基，即来自嗜糖假单胞菌的膜结合氢化酶的preHoxG蛋白，进行了系统最小化研究。与先前的假设不同，preHoxG能够激活H，因为它明显进行了催化氢/氘交换。然而，它并未执行[NiFe]氢化酶所描述的整个催化循环。值得注意的是，即使在存在O的情况下，preHoxG也能激活H，尽管位于小亚基中且被认为对耐O至关重要的独特[4Fe-3S]簇并不存在。这些发现挑战了目前对[NiFe]氢化酶耐O性的理解。本文讨论了这种最小化氢化酶在基础研究和应用研究中的适用性。
