Double‐Cubane [8Fe9S] Clusters ‐ a novel Nitrogenase‐related Cofactor in Biology

Three different types of electron-transferring metallo-ATPases are able to couple ATP hydrolysis to the reduction of low potential metal sites - energizing an electron. Besides the Fe-protein known from nitrogenase and homologous enzymes, two other kinds of ATPases with different scaffold and cofactors are used to achieve a uni-directional energetic uphill electron transfer to either reduce inactive Co-corrinoid containing proteins (RACE-type activators) or a second iron-sulfur cluster containing enzyme of a unique radical enzymes family (archerases). We have found a new cofactor in the latter enzyme family, which is a double-cubane cluster with two [4Fe4S]-subclusters bridged by a sulfido-ligand. An enzyme containing this cofactor catalyzes the ATP-dependent reduction of small molecules, including acetylene. Thus, enzymes containing the double-cubane cofactor are analogous in function and share some structural features with nitrogenases.