Crucial role and conservation of the three [2Fe-2S] clusters in the human mitochondrial ribosome.

Mitochondria synthesize only a small set of their proteins on endogenous mitoribosomes. These particles differ in structure and composition from both their bacterial 70S ancestors and cytosolic 80S ribosomes. Recently published high resolution structures of the human mitoribosome revealed the presence of three [2Fe-2S] clusters in the small and large subunits.

Two-stage binding of mitochondrial ferredoxin-2 to the core iron-sulfur cluster assembly complex.

Iron-sulfur (FeS) protein biogenesis in eukaryotes begins with the de novo assembly of [2Fe-2S] clusters by the mitochondrial core iron-sulfur cluster assembly (ISC) complex. 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 structural interaction of FDX2 with the complex remains unclear.

Mitochondrial [2Fe-2S] ferredoxins: new functions for old dogs.

Ferredoxins (FDXs) comprise a large family of iron-sulfur proteins that shuttle electrons from NADPH and FDX reductases into diverse biological processes. This review focuses on the structure, function and specificity of mitochondrial [2Fe-2S] FDXs that are related to bacterial FDXs due to their endosymbiotic inheritance. Their classical function in cytochrome P450-dependent steroid transformations was identified around 1960, and is exemplified by mammalian FDX1 (aka adrenodoxin).

Functional spectrum and specificity of mitochondrial ferredoxins FDX1 and FDX2.

Ferredoxins comprise a large family of iron-sulfur (Fe-S) proteins that shuttle electrons in diverse biological processes. Human mitochondria contain two isoforms of [2Fe-2S] ferredoxins, FDX1 (aka adrenodoxin) and FDX2, with known functions in cytochrome P450-dependent steroid transformations and Fe-S protein biogenesis. Here, we show that only FDX2, but not FDX1, is involved in Fe-S protein maturation.

The Radical SAM enzyme NirJ catalyzes the removal of two propionate side chains during heme d biosynthesis.

Heme d is a modified tetrapyrrole playing an important role in denitrification by acting as the catalytically essential cofactor in the cytochrome cd nitrite reductase of many denitrifying bacteria. In the course of heme d biosynthesis, the two propionate side chains on pyrrole rings A and B of the intermediate 12,18-didecarboxysiroheme are removed from the tetrapyrrole macrocycle. In the final heme d molecule, the propionate groups are replaced by two keto functions.

The PqqD homologous domain of the radical SAM enzyme ThnB is required for thioether bond formation during thurincin H maturation.

Thurincin H is a 31-residue, ribosomally synthesized bacteriocin originating from the thn operon of Bacillus thuringiensis SF361. It is the only known sactipeptide carrying four thioether bridges between four cysteines and the α-carbons of a serine, an asparagine and two threonine residues. By analysis of the thn operon and use of in vitro studies we now reveal that ThnB is a radical S-adenosylmethionine (SAM) enzyme containing two [4Fe-4S] clusters.