title: IscS from Archaeoglobus fulgidus has no desulfurase activity but may provide a cysteine ligand for [Fe2S2] cluster assembly.
abstract: Iron sulfur ([Fe-S]) clusters are essential prosthetic groups involved in fundamental cell processes such as gene expression regulation, electron transfer and Lewis acid base chemistry. Central components of their biogenesis are pyridoxal-5'-phosphate (PLP) dependent l-cysteine desulfurases, which provide the necessary S atoms for [Fe-S] cluster assembly. The archaeon Archaeoglobus fulgidus (Af) has two ORFs, which although annotated as l-cysteine desulfurases of the ISC type (IscS), lack the essential Lys residue (K199 in Af) that forms a Schiff base with PLP. We have previously determined the structure of an Af(IscU-D35A-IscS)2 complex heterologously expressed in Escherichia coli and found it to contain a [Fe2S2] cluster. In order to understand the origin of sulfide in that structure we have performed a series of functional tests using wild type and mutated forms of AfIscS. In addition, we have determined the crystal structure of an AfIscS-D199K mutant. From these studies we conclude that: i) AfIscS has no desulfurase activity; ii) in our in vitro [Fe2S2] cluster assembly experiments, sulfide ions are non-enzymatically generated by a mixture of iron, l-cysteine and PLP and iii) the physiological role of AfIscS may be to provide a cysteine ligand to the nascent cluster as observed in the [Fe2S2]-Af(IscU-D35A-IscS)2 complex. This article is part of a Special Issue entitled: Fe/S proteins: Analysis, structure, function, biogenesis and diseases.
authors.affiliation: Univ. Grenoble Alpes, IBS, F-38044 Grenoble, France; CNRS, IBS, F-38044 Grenoble, France; CEA, IBS, F-38044 Grenoble, France.
authors.forename: Adrien
authors.initials: A
authors.lastname: Pagnier
authors.affiliation: Univ. Grenoble Alpes, IBS, F-38044 Grenoble, France; CNRS, IBS, F-38044 Grenoble, France; CEA, IBS, F-38044 Grenoble, France.
authors.forename: Yvain
authors.initials: Y
authors.lastname: Nicolet
authors.affiliation: Univ. Grenoble Alpes, IBS, F-38044 Grenoble, France; CNRS, IBS, F-38044 Grenoble, France; CEA, IBS, F-38044 Grenoble, France. Electronic address: juan.fontecilla@ibs.fr.
authors.forename: Juan C
authors.initials: JC
authors.lastname: Fontecilla-Camps
mesh_terms: D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019611:Archaeoglobus fulgidus / Q000201:enzymology* / Q000235:genetics; D013437:Carbon-Sulfur Lyases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007501:Iron / Q000737:chemistry / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011732:Pyridoxal Phosphate / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013440:Sulfides / Q000737:chemistry / Q000378:metabolism
chemical_list: D019843:Archaeal Proteins; D007506:Iron-Sulfur Proteins; D008024:Ligands; D050505:Mutant Proteins; D013440:Sulfides; D011732:Pyridoxal Phosphate; D007501:Iron; D013437:Carbon-Sulfur Lyases; C080546:cysteine desulfurase; D003545:Cysteine
keywords: 5′-pyridoxamine; Archaeoglobus fulgidus; IscS; Pyridoxal 5′-phosphate; Schiff base; l-cysteine desulfurase