43 research outputs found
Two-dimensional pulsed electron spin resonance characterization of 15N-labeled archaeal Rieske-type ferredoxin
AbstractTwo-dimensional electron spin-echo envelope modulation (ESEEM) analysis of the uniformly 15N-labeled archaeal Rieske-type [2Fe–2S] ferredoxin (ARF) from Sulfolobus solfataricus P1 has been conducted in comparison with the previously characterized high-potential protein homologs. Major differences among these proteins were found in the hyperfine sublevel correlation (HYSCORE) lineshapes and intensities of the signals in the (++) quadrant, which are contributed from weakly coupled (non-coordinated) peptide nitrogens near the reduced clusters. They are less pronounced in the HYSCORE spectra of ARF than those of the high-potential protein homologs, and may account for the tuning of Rieske-type clusters in various redox systems
Sensing iron availability via the fragile [4Fe-4S] cluster of the bacterial transcriptional repressor RirA
Rhizobial iron regulator A (RirA) is a global regulator of iron homeostasis in many nitrogen-fixing Rhizobia and related species of α-proteobacteria. It belongs to the widespread Rrf2 super-family of transcriptional regulators and features three conserved Cys residues that characterise the binding of an iron–sulfur cluster in other Rrf2 family regulators. Here we report biophysical studies demonstrating that RirA contains a [4Fe–4S] cluster, and that this form of the protein binds RirA-regulated DNA, consistent with its function as a repressor of expression of many genes involved in iron uptake. Under low iron conditions, [4Fe–4S] RirA undergoes a cluster conversion reaction resulting in a [2Fe–2S] form, which exhibits much lower affinity for DNA. Under prolonged low iron conditions, the [2Fe–2S] cluster degrades to apo-RirA, which does not bind DNA and can no longer function as a repressor of the cell's iron-uptake machinery. [4Fe–4S] RirA was also found to be sensitive to O2, suggesting that both iron and O2 are important signals for iron metabolism. Consistent with this, in vivo data showed that expression of RirA-regulated genes is also affected by O2. These data lead us to propose a novel regulatory model for iron homeostasis, in which RirA senses iron via the incorporation of a fragile iron–sulfur cluster that is sensitive to iron and O2 concentrations
Structure and Molecular Evolution of CDGSH Iron-Sulfur Domains
The recently discovered CDGSH iron-sulfur domains (CISDs) are classified into seven major types with a wide distribution throughout the three domains of life. The type 1 protein mitoNEET has been shown to fold into a dimer with the signature CDGSH motif binding to a [2Fe-2S] cluster. However, the structures of all other types of CISDs were unknown. Here we report the crystal structures of type 3, 4, and 6 CISDs determined at 1.5 Å, 1.8 Å and 1.15 Å resolution, respectively. The type 3 and 4 CISD each contain one CDGSH motif and adopt a dimeric structure. Although similar to each other, the two structures have permutated topologies, and both are distinct from the type 1 structure. The type 6 CISD contains tandem CDGSH motifs and adopts a monomeric structure with an internal pseudo dyad symmetry. All currently known CISD structures share dual iron-sulfur binding modules and a β-sandwich for either intermolecular or intramolecular dimerization. The iron-sulfur binding module, the β-strand N-terminal to the module and a proline motif are conserved among different type structures, but the dimerization module and the interface and orientation between the two iron-sulfur binding modules are divergent. Sequence analysis further shows resemblance between CISD types 4 and 7 and between 1 and 2. Our findings suggest that all CISDs share common ancestry and diverged into three primary folds with a characteristic phylogenetic distribution: a eukaryote-specific fold adopted by types 1 and 2 proteins, a prokaryote-specific fold adopted by types 3, 4 and 7 proteins, and a tandem-motif fold adopted by types 5 and 6 proteins. Our comprehensive structural, sequential and phylogenetic analysis provides significant insight into the assembly principles and evolutionary relationship of CISDs
<i>Strongyloides</i> questions-a research agenda for the future.
The Strongyloides genus of parasitic nematodes have a fascinating life cycle and biology, but are also important pathogens of people and a World Health Organization-defined neglected tropical disease. Here, a community of Strongyloides researchers have posed thirteen major questions about Strongyloides biology and infection that sets a Strongyloides research agenda for the future. This article is part of the Theo Murphy meeting issue 'Strongyloides: omics to worm-free populations'
Analysis of covalent flavinylation using thermostable succinate dehydrogenase from Thermus thermophilus and Sulfolobus tokodaii lacking SdhE homologs
AbstractRecent studies have indicated that post-translational flavinylation of succinate dehydrogenase subunit A (SdhA) in eukaryotes and bacteria require the chaperone-like proteins Sdh5 and SdhE, respectively. How does covalent flavinylation occur in prokaryotes, which lack SdhE homologs? In this study, I showed that covalent flavinylation in two hyperthermophilic bacteria/archaea lacking SdhE, Thermus thermophilus and Sulfolobus tokodaii, requires heat and dicarboxylic acid. These thermophilic bacteria/archaea inhabit hot environments and are said to be genetically far removed from mesophilic bacteria which possess SdhE. Since mesophilic bacteria have been effective at covalent bonding in temperate environments, they may have caused the evolution of SdhE
An Open Generic Transporter Specification for the Plural Node Architecture of Professional Audio Devices
The Plural Node architecture is an implementation architecture for professional audio devices that adhere to the “Audio and Music (A/M)” protocol. The A/M protocol determines how audio and MIDI data are transported over IEEE 1394 (firewire). The Plural-Node implementation architecture comprises two components on separate IEEE 1394 nodes – a “Transporter” component dedicated to A/M protocol handling, and an “Enabler” component that controls the Transporter and provides high level plug abstractions. Low level control of individual Transporters occurs within the “Hardware Abstraction Layer” (HAL) of the Enabler. Device manufacturers write their own plug-ins for the HAL to interact with their Transporters. The Open Generic Transporter specification provides an open interface between the HAL and Transporter for the convenience of device manufacturers
Crystallization and preliminary X-ray diffraction studies of the prototypal homologue of mitoNEET (Tth-NEET0026) from the extreme thermophile Thermus thermophilus HB8
A thermophilic bacterial homologue of mitoNEET (a mammalian mitochondrial outer membrane protein) from T. thermophilus HB8 (open reading frame TTHA0026; Tth-NEET0026) has been identified as a water-soluble prototypal [2Fe–2S] protein and crystallized. The bipyramidal crystals of the recombinant Tth-NEET0026 diffracted to 1.80 Å resolution using synchrotron radiation