Formation of a Nitrogenase P‐cluster [Fe₈S₇] Core via Reductive Fusion of Two All‐Ferric [Fe₄S₄] Clusters

Abstract

How does your cluster grow? The nitrogenase P‐cluster [Fe8S7] core has been assembled from the two all‐ferric [Fe4S4] clusters via phosphine desulfurization. This finding suggests that reductive desulfurization from an [Fe4S4] cluster can occur in the maturation process of the P‐cluster of nitrogenase.

Developments in the Biomimetic Chemistry of Cubane-Type and Higher Nuclearity Iron–Sulfur Clusters

“…A second assembly system in which Et 3 PS replaces SC(NMe 2 ) 2 affords [Fe 8 S 7 {N(SiMe 3 ) 2 } 4 (SPEt 3 ) 2 ] ( 77b , 70%). 79 Another synthetic protocol for this cluster is the reaction of [Fe 4 S 4 {N(SiMe 3 ) 2 } 4 ] with Et 3 P in toluene (29%). Sulfide appears to be removed as S 0 from the initial cluster core, a rare reaction for any iron-sulfur cluster that is likely facilitated in this instance by the all-ferric oxidation state of the precursor.…”

Nitrogenase assembly

“…This hypothesis was supported indirectly by the earlier recovery of [Fe 4 S 4 ] fragments from P-cluster extraction attempts [2], as well as the recent success in chemically synthesizing P-cluster topologs from 4Fe precursors [21–27]. The direct biological proof for this theory, however, came from the characterization of two NifDK variants of A. vinelandii : one, designated Δ nifB NifDK, was isolated from a nifB -deletion background; the other, designated Δ nifH NifDK, was isolated from a nifH -deletion background.…”

“…XAS analyses demonstrate that the Fe atoms of the clusters undergo successive reduction upon maturation till they eventually stabilize at a near all-ferrous oxidation state [30], further illustrating that this process involves the reductive coupling of two 4Fe units into an 8Fe entity. The chemical details of this process are yet to be defined; however, it was reported recently that an [Fe 8 S 7 ] core could be synthesized chemically from two all-ferric [Fe 4 S 4 ] clusters via phosphine desulfurization [27]. This observation suggests a plausible mechanism of P-cluster maturation that involves the reductive desulfurization of an [Fe 4 S 4 ] cluster.…”

Biosynthesis of Nitrogenase Metalloclusters

“…Recently, it was reported that an [Fe 8 S 7 ] core could be chemically synthesized from two all-ferric [Fe 4 S 4 ] clusters via phosphine desulfurization. 112 By analogy, biosynthesis of the P-cluster could also involve the reductive desulfurization of one [Fe 4 S 4 ] subcluster. Alternatively, if one of the two 4Fe subclusters is in fact ligated by three S atoms and one light atom ( e.g.…”