C1q is a versatile recognition protein that binds to an amazing variety of immune and non-immune ligands triggers activation the classical pathway complement. The crystal structure globular domain responsible for its properties has now been solved refined 1.9 Å resolution. reveals compact, almost spherical heterotrimeric assembly held together mainly by non-polar interactions, with Ca2+ ion bound at top. appears be key factor this protein. Plausible three-dimensional models in complex two...

Abstract Efficient apoptotic cell clearance is critical for maintenance of tissue homeostasis, and to control the immune responses mediated by phagocytes. Little known about molecules that contribute “eat me” signals on surface. C1q, recognition unit C1 complex complement, also senses altered structures from self a major actor tolerance. HeLa cells were rendered UV-B treatment variety cellular molecular approaches used investigate nature target(s) recognized C1q. Using surface plasmon...

The crystal structure of the membrane-bound O 2 -tolerant [NiFe]-hydrogenase 1 from Escherichia coli ( Ec Hyd-1) has been solved in three different states: as-isolated, H -reduced, and chemically oxidized. As very recently reported for similar enzymes Ralstonia eutropha Hydrogenovibrio marinus , two supernumerary Cys residues coordinate proximal [FeS] cluster Hyd-1, which lacks one inorganic sulfide ligands. We find that aerobically purified species contains a mixture at least conformations...

Most bacteriophages present a tail allowing host recognition, cell wall perforation, and viral DNA channeling from the capsid to infected bacterium cytoplasm. The majority of tailed phages bear long flexible ( Siphoviridae ) at tip which receptor binding proteins (RBPs) specifically interact with their host, triggering infection. In siphophage T5, unique RBP is located extremity central fiber. We structures T5 tip, determined by cryo–electron microscopy before after interaction its E. coli...

Abstract NsrR from Streptomyces coelicolor ( Sc) regulates the expression of three genes through progressive degradation its [4Fe–4S] cluster on nitric oxide (NO) exposure. We report 1.95 Å resolution crystal structure dimeric holo-ScNsrR and show that is coordinated by invariant Cys residues one monomer and, unexpectedly, Asp8 other. A cavity map suggests NO displaces as a ligand while D8A D8C variants remain sensitive, DNA binding affected. structural comparison with an apo-IscR-DNA...

We have observed the photoactivatable fluorescent protein IrisFP in a transient dark state with near-atomic resolution. This is assigned to radical species that either relaxes ground or evolves into permanently bleached chromophore. took advantage of X-rays populate radical, which presumably forms under illumination visible light by an electron-transfer reaction triplet state. The combined X-ray diffraction and crystallo UV−vis absorption, fluorescence, Raman data reveal formation involves...

The dimerization of the O 2 sensor FNR is regulated by extremely fine-tuned interactions.

The recently discovered Rrf2 family transcriptional regulator RsrR coordinates a [2Fe–2S] cluster. Remarkably, binding of the protein to RsrR-regulated promoter DNA sequences is switched on and off through facile cycling cluster between +2 +1 states. Here, we report high resolution crystal structures dimer, revealing that asymmetrically coordinated across monomer–monomer interface by two Cys residues from one subunit His Glu other. To our knowledge, this first example bound [Fe–S] with three...

Quinolinate synthase (NadA) is a Fe4S4 cluster-containing dehydrating enzyme involved in the synthesis of quinolinic acid (QA), universal precursor essential nicotinamide adenine dinucleotide (NAD) coenzyme. A previously determined apo NadA crystal structure revealed binding one substrate analog, providing partial mechanistic information. Here, we report on holo X-ray NadA. The presence cluster generates an internal tunnel and cavity which have docked last to be dehydrated form QA. We find...

The Escherichia coli fumarate and nitrate reduction (FNR) regulator acts as the cell’s master switch for transition between anaerobic aerobic respiration, controlling expression of >300 genes in response to O2 availability. Oxygen is perceived through a reaction with FNR’s [4Fe-4S] cluster cofactor. In addition its primary signal, FNR also reacts nitric oxide (NO). physiological concentrations NO, de-represses transcription hmp, which encodes principal NO-detoxifying enzyme, fails...

The enzyme NadA catalyzes the synthesis of quinolinic acid (QA), precursor universal nicotinamide adenine dinucleotide (NAD) cofactor. Here, we report crystal structures complexes between Thermotoga maritima (Tm) K219R/Y107F variant and (i) first intermediate (W) resulting from condensation dihydroxyacetone phosphate (DHAP) with iminoaspartate (ii) DHAP analogue triose-phosphate isomerase inhibitor phosphoglycolohydroxamate (PGH). In addition, using TmNadA K219R/Y21F variant, have reacted...

Ni-dependent acetyl-CoA synthase (ACS) and CO dehydrogenase (CODH) constitute the central enzyme complex of Wood−Ljungdahl pathway formation. The crystal structure a recombinant bacterial ACS lacking N-terminal domain that interacts with CODH shows large reorganization remaining two globular domains, producing narrow cleft suitable size, shape, nature to bind CoA. Sequence comparisons homologous archaeal enzymes naturally lack show many amino acids lining this are conserved. Besides typical...

NadA is a multifunctional enzyme that condenses dihydroxyacetone phosphate (DHAP) with iminoaspartate (IA) to generate quinolinic acid (QA), the universal precursor of nicotinamide adenine dinucleotide (NAD(P)) cofactor. Using X-ray crystallography, we have (i) characterized two reaction intermediates QA synthesis using "pH-shift" approach and slowly reacting Thermotoga maritima variant (ii) observed product, resulting from degradation an intermediate analogue, bound close entrance long...

A combined experimental and computational study of an O₂-tolerant [NiFe]-hydrogenase mutated proximal FeS cluster with possible applications to similar problems.

Iron-regulatory proteins (IRPs) 1 and 2 are closely related molecules involved in animal iron metabolism. Both can bind to specific mRNA regions called iron-responsive elements thereby control the expression of uptake, storage utilization iron. In iron-replete cells, IRP1, but not IRP2, binds a [4Fe–4S] cluster functions as cytoplasmic aconitase, with simultaneous loss its RNA-binding ability. Whereas IRP2 is known be Fe homeostasis, role IRP1 less clear; it may provide link between citrate...

Abstract The vast majority of bacteriophages (phages) - bacterial viruses present a tail that allows host recognition, cell wall perforation and safe channelling the viral DNA from capsid to cytoplasm infected bacterium. tailed phages bears long flexible ( Siphoviridae ) at distal end which tip complex, often called baseplate, harbours one or more Receptor Binding Protein·s (RBPs). Interaction between RBPs surface triggers ejection, but little is known on these mechanisms for . Here, we...

Quinolinate synthase (NadA) is a [4Fe-4S] cluster-containing enzyme involved in the formation of quinolinic acid, precursor essential NAD coenzyme. Here, we report synthesis and activity derivatives first inhibitor NadA. Using multidisciplinary approaches have investigated their action mechanism discovered additional specific inhibitors this enzyme.