Rôles émergents des lipides naturels et artificiels dans l'élaboration de la fonction catalytique, la stabilité et l'état d'oligomerisation des protéines membranaires

The study of biological membranes involves the examination of the different properties of its main components: as lipids and proteins. In this manuscript, the lipid-lipid interaction and the lipid-protein interaction were monitored by vibrational spectroscopy (Raman and Infrared). We have been interested in the first part in studying the structure and organization of phospholipids in the gel phase and the liquid crystalline phase using mid infrared spectroscopy. In addition, the effect of the head group composition on the hydrogen bonding behaviour of lipid mixtures was probed using far infrared spectroscopy. In the second part, the interaction of the NADH ubiquinone oxidoreductase protein and NuoL mutant (D563N) with zinc was investigated through FTIR difference spectroscopy where the conformational changes upon zinc binding were monitored. Finally, the metal-ligand vibrations of the iron- sulfur clusters in NuoB mutants (C64A G100C) at different pH were analysed using Raman spectroscopy.L'étude des membranes biologiques nécessite l'examen des différentes propriétés de ses composantes principales: les lipides et les protéines. Dans ce manuscrit, l'interaction lipide- lipide et lipide-protéine ont été suivies par spectroscopie vibrationnelle (Raman, Infrarouge). Nous sommes intéressés en premier lieu à l'étude de la structure et l'organisation des phospholipides dans leur phase gel et leur phase cristalline liquide en utilisant la spectroscopie moyen infrarouge. En outre, l'effet de la composition du groupement hydrophiles des lipides sur le comportement de la liaison hydrogène des mélanges lipidiques a été sondé en utilisant la spectroscopie lointain infrarouge. Dans la seconde partie, l'interaction de la protéine NADH ubiquinone oxydoréductase et du mutant NuoL (D563N) avec le zinc ont été étudiés par spectroscopie différentielle et les changements conformationnels induits par la liaison du zinc avec les protéines ont été examinés. Enfin, les vibrations métal-ligand des groupements fer-soufre dans le mutant de NuoB (C64A G100C) à différents pH ont été analysées par spectroscopie Raman

Mechanism of Iron-Sulfur Cluster Assembly: In the Intimacy of Iron and Sulfur Encounter

Place: Basel Publisher: Mdpi WOS:000586852600001Iron-sulfur (Fe-S) clusters are protein cofactors of a multitude of enzymes performing essential biological functions. Specialized multi-protein machineries present in all types of organisms support their biosynthesis. These machineries encompass a scaffold protein on which Fe-S clusters are assembled and a cysteine desulfurase that provides sulfur in the form of a persulfide. The sulfide ions are produced by reductive cleavage of the persulfide, which involves specific reductase systems. Several other components are required for Fe-S biosynthesis, including frataxin, a key protein of controversial function and accessory components for insertion of Fe-S clusters in client proteins. Fe-S cluster biosynthesis is thought to rely on concerted and carefully orchestrated processes. However, the elucidation of the mechanisms of their assembly has remained a challenging task due to the biochemical versatility of iron and sulfur and the relative instability of Fe-S clusters. Nonetheless, significant progresses have been achieved in the past years, using biochemical, spectroscopic and structural approaches with reconstituted system in vitro. In this paper, we review the most recent advances on the mechanism of assembly for the founding member of the Fe-S cluster family, the [2Fe2S] cluster that is the building block of all other Fe-S clusters. The aim is to provide a survey of the mechanisms of iron and sulfur insertion in the scaffold proteins by examining how these processes are coordinated, how sulfide is produced and how the dinuclear [2Fe2S] cluster is formed, keeping in mind the question of the physiological relevance of the reconstituted systems. We also cover the latest outcomes on the functional role of the controversial frataxin protein in Fe-S cluster biosynthesis

Unravelling successive steps in Fe−S cluster biosynthesis by the mitochondrial ISC machinery: contributions from NMR focusing on the ISCU/IscU scaffold protein

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Evidence for [2Fe-2S] 2+ and Linear [3Fe-4S] 1+ Clusters in a Unique Family of Glycine/Cysteine-Rich Fe-S Proteins from Megavirinae Giant Viruses

International audienceWe have discovered a protein with an amino acid composition exceptionally rich in glycine and cysteine residues in the giant virus mimivirus. This small 6 kDa protein is among the most abundant proteins in the icosahedral 0.75 μm viral particles; it has no predicted function but is probably essential for infection. The aerobically purified red-brownish protein overproduced inEscherichia coli contained both iron and inorganic sulfide. UV/vis, EPR, and Mössbauer studies revealed that the viral protein, coined GciS, accommodated two distinct Fe-S clusters: a diamagnetic S = 0 [2Fe-2S]2+ cluster and a paramagnetic S = 5/2 linear [3Fe-4S]1+ cluster, a geometry rarely stabilized in native proteins. Orthologs of mimivirus GciS were identified within all clades of Megavirinae, a Mimiviridae subfamily infecting Acanthamoeba, including the distantly related tupanviruses, and displayed the same spectroscopic features. Thus, these glycine/cysteine-rich proteins form a new family of viral Fe-S proteins sharing unique Fe-S cluster binding properties

Unique Biradical Intermediate in the Mechanism of the Heme Enzyme Chlorite Dismutase

Funding Information: This research was supported by the grant NWO–CW 711.014.006 from the Council for Chemical Sciences of The Netherlands Organization for Scientific Research. S.T. acknowledges the support from the Project LISBOA-01-0145-FEDER-007660 (Microbiologia Molecular, Estrutural e Celular) funded by FEDER funds through COMPETE 2020─Programa Operacional Competitividade e Internacionalização (POCI) and by national funds through FCT─Fundação para a Ciência e a Tecnologia and from the European Union’s Horizon 2020 Research and Innovation Program through TIMB3 (grant agreements no 810856). This work is dedicated to the late Prof. Simon de Vries, who pioneered the development of the rapid kinetic techniques that have been seminal in this study. Publisher Copyright: © 2021 The Authors. Published by American Chemical Society.The heme enzyme chlorite dismutase (Cld) catalyzes O-O bond formation as part of the conversion of the toxic chlorite (ClO2-) to chloride (Cl-) and molecular oxygen (O2). Enzymatic O-O bond formation is rare in nature, and therefore, the reaction mechanism of Cld is of great interest. Microsecond timescale pre-steady-state kinetic experiments employing Cld from Azospira oryzae (AoCld), the natural substrate chlorite, and the model substrate peracetic acid (PAA) reveal the formation of distinct intermediates. AoCld forms a complex with PAA rapidly, which is cleaved heterolytically to yield Compound I, which is sequentially converted to Compound II. In the presence of chlorite, AoCld forms an initial intermediate with spectroscopic characteristics of a 6-coordinate high-spin ferric substrate adduct, which subsequently transforms at kobs = 2-5 × 104 s-1 to an intermediate 5-coordinated high-spin ferric species. Microsecond-timescale freeze-hyperquench experiments uncovered the presence of a transient low-spin ferric species and a triplet species attributed to two weakly coupled amino acid cation radicals. The intermediates of the chlorite reaction were not observed with the model substrate PAA. These findings demonstrate the nature of physiologically relevant catalytic intermediates and show that the commonly used model substrate may not behave as expected, which demands a revision of the currently proposed mechanism of Clds. The transient triplet-state biradical species that we designate as Compound T is, to the best of our knowledge, unique in heme enzymology. The results highlight electron paramagnetic resonance spectroscopic evidence for transient intermediate formation during the reaction of AoCld with its natural substrate chlorite. In the proposed mechanism, the heme iron remains ferric throughout the catalytic cycle, which may minimize the heme moiety's reorganization and thereby maximize the enzyme's catalytic efficiency.publishersversionpublishe

Evidence for [2Fe-2S] 2+ and Linear [3Fe-4S] 1+ Clusters in a Unique Family of Glycine/Cysteine-Rich Fe-S Proteins from Megavirinae Giant Viruses

International audienceWe have discovered a protein with an amino acid composition exceptionally rich in glycine and cysteine residues in the giant virus mimivirus. This small 6 kDa protein is among the most abundant proteins in the icosahedral 0.75 μm viral particles; it has no predicted function but is probably essential for infection. The aerobically purified red-brownish protein overproduced inEscherichia coli contained both iron and inorganic sulfide. UV/vis, EPR, and Mössbauer studies revealed that the viral protein, coined GciS, accommodated two distinct Fe-S clusters: a diamagnetic S = 0 [2Fe-2S]2+ cluster and a paramagnetic S = 5/2 linear [3Fe-4S]1+ cluster, a geometry rarely stabilized in native proteins. Orthologs of mimivirus GciS were identified within all clades of Megavirinae, a Mimiviridae subfamily infecting Acanthamoeba, including the distantly related tupanviruses, and displayed the same spectroscopic features. Thus, these glycine/cysteine-rich proteins form a new family of viral Fe-S proteins sharing unique Fe-S cluster binding properties

A traffic light enzyme: acetate binding reversibly switches chlorite dismutase from a red- to a green-colored heme protein

Chlorite dismutase is a unique heme enzyme that catalyzes the conversion of chlorite to chloride and molecular oxygen. The enzyme is highly specific for chlorite but has been known to bind several anionic and neutral ligands to the heme iron. In a pH study, the enzyme changed color from red to green in acetate buffer pH 5.0. The cause of this color change was uncovered using UV-visible and EPR spectroscopy. Chlorite dismutase in the presence of acetate showed a change of the UV-visible spectrum: a redshift and hyperchromicity of the Soret band from 391 to 404 nm and a blueshift of the charge transfer band CT1 from 647 to 626 nm. Equilibrium binding titrations with acetate resulted in a dissociation constant of circa 20 mM at pH 5.0 and 5.8. EPR spectroscopy showed that the acetate bound form of the enzyme remained high spin S = 5/2, however with an apparent change of the rhombicity and line broadening of the spectrum. Mutagenesis of the proximal arginine Arg183 to alanine resulted in the loss of the ability to bind acetate. Acetate was discovered as a novel ligand to chlorite dismutase, with evidence of direct binding to the heme iron. The green color is caused by a blueshift of the CT1 band that is characteristic of the high spin ferric state of the enzyme. Any weak field ligand that binds directly to the heme center may show the red to green color change, as was indeed the case for fluoride

Evidence for [2Fe-2S] 2+ and Linear [3Fe-4S] 1+ Clusters in a Unique Family of Glycine/Cysteine-Rich Fe-S Proteins from Megavirinae Giant Viruses

International audienceWe have discovered a protein with an amino acid composition exceptionally rich in glycine and cysteine residues in the giant virus mimivirus. This small 6 kDa protein is among the most abundant proteins in the icosahedral 0.75 μm viral particles; it has no predicted function but is probably essential for infection. The aerobically purified red-brownish protein overproduced inEscherichia coli contained both iron and inorganic sulfide. UV/vis, EPR, and Mössbauer studies revealed that the viral protein, coined GciS, accommodated two distinct Fe-S clusters: a diamagnetic S = 0 [2Fe-2S]2+ cluster and a paramagnetic S = 5/2 linear [3Fe-4S]1+ cluster, a geometry rarely stabilized in native proteins. Orthologs of mimivirus GciS were identified within all clades of Megavirinae, a Mimiviridae subfamily infecting Acanthamoeba, including the distantly related tupanviruses, and displayed the same spectroscopic features. Thus, these glycine/cysteine-rich proteins form a new family of viral Fe-S proteins sharing unique Fe-S cluster binding properties