A cross-kingdom conserved ER-phagy receptor maintains endoplasmic reticulum homeostasis during stress.

Eukaryotes have evolved various quality control mechanisms to promote proteostasis in the endoplasmic reticulum (ER). Selective removal of certain ER domains via autophagy (termed as ER-phagy) has emerged as a major quality control mechanism. However, the degree to which ER-phagy is employed by other branches of ER-quality control remains largely elusive.

A conformation-specific ON-switch for controlling CAR T cells with an orally available drug.

Molecular ON-switches in which a chemical compound induces protein-protein interactions can allow cellular function to be controlled with small molecules. ON-switches based on clinically applicable compounds and human proteins would greatly facilitate their therapeutic use. Here, we developed an ON-switch system in which the human retinol binding protein 4 (hRBP4) of the lipocalin family interacts with engineered hRBP4 binders in a small molecule-dependent manner.

The leucine-rich repeat domain of human peroxidasin 1 promotes binding to laminin in basement membranes.

Human peroxidasin 1 (PXDN) is a homotrimeric multidomain heme peroxidase and essential for tissue development and architecture. It has a biosynthetic function and catalyses the hypobromous acid-mediated formation of specific covalent sulfilimine (SN) bonds, which cross-link type IV collagen chains in basement membranes. Currently, it is unknown whether and which domain(s) [i.

Molecular Mechanism of Enzymatic Chlorite Detoxification: Insights from Structural and Kinetic Studies.

The heme enzyme chlorite dismutase (Cld) catalyzes the degradation of chlorite to chloride and dioxygen. Although structure and steady-state kinetics of Clds have been elucidated, many questions remain (e.g.

Hydrogen peroxide-mediated conversion of coproheme to heme b by HemQ-lessons from the first crystal structure and kinetic studies.

Unlabelled: Heme biosynthesis in Gram-positive bacteria follows a recently described coproporphyrin-dependent pathway with HemQ catalyzing the decarboxylation of coproheme to heme b. Here we present the first crystal structure of a HemQ (homopentameric coproheme-HemQ from Listeria monocytogenes) at 1.69 Å resolution and the conversion of coproheme to heme b followed by UV-vis and resonance Raman spectroscopy as well as mass spectrometry.

Chemistry and Molecular Dynamics Simulations of Heme b-HemQ and Coproheme-HemQ.

Recently, a novel pathway for heme b biosynthesis in Gram-positive bacteria has been proposed. The final poorly understood step is catalyzed by an enzyme called HemQ and includes two decarboxylation reactions leading from coproheme to heme b. Coproheme has been suggested to act as both substrate and redox active cofactor in this reaction.

From chlorite dismutase towards HemQ - the role of the proximal H-bonding network in haeme binding.

Chlorite dismutase (Cld) and HemQ are structurally and phylogenetically closely related haeme enzymes differing fundamentally in their enzymatic properties. Clds are able to convert chlorite into chloride and dioxygen, whereas HemQ is proposed to be involved in the haeme b synthesis of Gram-positive bacteria. A striking difference between these protein families concerns the proximal haeme cavity architecture.

Mechanism of chlorite degradation to chloride and dioxygen by the enzyme chlorite dismutase.

Heme b containing chlorite dismutase (Cld) catalyses the conversion of chlorite to chloride and dioxygen which includes an unusual OO bond formation. This review summarizes our knowledge about the interaction of chlorite with heme enzymes and introduces the biological role, phylogeny and structure of functional chlorite dismutases with differences in overall structure and subunit architecture. The paper sums up the available experimental and computational studies on chlorite degradation by water soluble porphyrin complexes as well as a model based on the active site of Cld.

Dimeric chlorite dismutase from the nitrogen-fixing cyanobacterium Cyanothece sp. PCC7425.

It is demonstrated that cyanobacteria (both azotrophic and non-azotrophic) contain heme b oxidoreductases that can convert chlorite to chloride and molecular oxygen (incorrectly denominated chlorite 'dismutase', Cld). Beside the water-splitting manganese complex of photosystem II, this metalloenzyme is the second known enzyme that catalyses the formation of a covalent oxygen-oxygen bond. All cyanobacterial Clds have a truncated N-terminus and are dimeric (i.

Structure and heme-binding properties of HemQ (chlorite dismutase-like protein) from Listeria monocytogenes.

Chlorite dismutase-like proteins are structurally closely related to functional chlorite dismutases which are heme b-dependent oxidoreductases capable of reducing chlorite to chloride with simultaneous production of dioxygen. Chlorite dismutase-like proteins are incapable of performing this reaction and their biological role is still under discussion. Recently, members of this large protein family were shown to be involved in heme biosynthesis in Gram-positive bacteria, and thus the protein was renamed HemQ in these organisms.

Independent evolution of four heme peroxidase superfamilies.

Four heme peroxidase superfamilies (peroxidase-catalase, peroxidase-cyclooxygenase, peroxidase-chlorite dismutase and peroxidase-peroxygenase superfamily) arose independently during evolution, which differ in overall fold, active site architecture and enzymatic activities. The redox cofactor is heme b or posttranslationally modified heme that is ligated by either histidine or cysteine. Heme peroxidases are found in all kingdoms of life and typically catalyze the one- and two-electron oxidation of a myriad of organic and inorganic substrates.

Transiently produced hypochlorite is responsible for the irreversible inhibition of chlorite dismutase.

Chlorite dismutases (Clds) are heme b-containing prokaryotic oxidoreductases that catalyze the reduction of chlorite to chloride with the concomitant release of molecular oxygen. Over time, they are irreversibly inactivated. To elucidate the mechanism of inactivation and investigate the role of the postulated intermediate hypochlorite, the pentameric chlorite dismutase of "Candidatus Nitrospira defluvii" (NdCld) and two variants (having the conserved distal arginine 173 exchanged with alanine and lysine) were recombinantly produced in Escherichia coli.

Chlorite dismutases - a heme enzyme family for use in bioremediation and generation of molecular oxygen.

Chlorite is a serious environmental concern, as rising concentrations of this harmful anthropogenic compound have been detected in groundwater, drinking water, and soil. Chlorite dismutases (Clds) are therefore important molecules in bioremediation as Clds catalyze the degradation of chlorite to chloride and molecular oxygen. Clds are heme b-containing oxidoreductases present in numerous bacterial and archaeal phyla.

Manipulating conserved heme cavity residues of chlorite dismutase: effect on structure, redox chemistry, and reactivity.

Chlorite dismutases (Clds) are heme b containing oxidoreductases that convert chlorite to chloride and molecular oxygen. In order to elucidate the role of conserved heme cavity residues in the catalysis of this reaction comprehensive mutational and biochemical analyses of Cld from "Candidatus Nitrospira defluvii" (NdCld) were performed. Particularly, point mutations of the cavity-forming residues R173, K141, W145, W146, and E210 were performed.