Biology subjects

Steinhilper, R.

Publications and source records attributed to Steinhilper, R..

2 recordsLinked to original sources

bioRxiv2024

Structural evidence for two-stage binding of mitochondrial ferredoxin 2 to the core iron-sulfur cluster assembly complex

Iron-sulfur (FeS) clusters are ubiquitous metallocofactors that are essential for life. In eukaryotes, FeS cluster biosynthesis begins with the de novo assembly of a [2Fe-2S] cluster by the core iron-sulfur cluster assembly (ISC) complex in the mitochondrial matrix. This complex comprises the scaffold protein ISCU2, the cysteine desulfurase subcomplex NFS1-ISD11-ACP1, the allosteric activator frataxin (FXN) and the electron donor ferredoxin 2 (FDX2). The interaction of FDX2 with the complex remains unclear. Here, we present cryo-EM structures of the FDX2-bound core ISC complex and show that FDX2 and FXN compete for overlapping binding sites during [2Fe-2S] cluster biosynthesis. FDX2 binds in two conformations; in the distal conformation, helix F of FDX2 shows loose electrostatic interaction with an arginine patch of NFS1, while in the proximal conformation this interaction tightens and the FDX2-specific C terminus forms contacts with NFS1; in this conformation, the [2Fe-2S] cluster of FDX2 is close enough to the ISCU2 FeS cluster assembly site for rapid electron transfer.

biophysics↗

bioRxiv2022

Structure of the membrane-bound formate hydrogenlyase complex from Escherichia coli

The prototypical hydrogen-producing enzyme, the membrane-bound formate hydrogen lyase (FHL) complex from Escherichia coli, links formate oxidation at a molybdopterin-containing formate dehydrogenase to proton reduction at a [NiFe] hydrogenase. It is of intense interest due to its ability to efficiently produce H2 during fermentation, its reversibility, allowing H2-dependent CO2 reduction, and its evolutionary link to respiratory complex I. FHL has been studied for over a century, but its atomic structure remains unknown. Here we report cryo-EM structures of FHL in its aerobically- and anaerobically-isolated forms at resolutions reaching 2.6 [A]. This includes well-resolved density for conserved loops linking the soluble and membrane arms believed to be essential in coupling enzymatic turnover to ion translocation across the membrane in the complex I superfamily. We describe an unpredicted metal-binding site near the interface of FdhF and HycF subunits that may play a role in preventing reverse activity in vivo, and evaluate possible structural determinants of the bias toward hydrogen production over its oxidation.

biophysics↗