title: The SoxYZ complex carries sulfur cycle intermediates on a peptide swinging arm.
abstract: The bacterial Sox (sulfur oxidizing) system allows the utilization of inorganic sulfur compounds in energy metabolism. Central to this process is the SoxYZ complex that carries the pathway intermediates on a cysteine residue near the C terminus of SoxY. Crystal structures have been determined for Paracoccus pantotrophus SoxYZ with the carrier cysteine in the underivatized state, conjugated to the polysulfide mimic beta-mercaptoethanol, and as the sulfonate adduct pathway intermediate. The carrier cysteine is located on a peptide swinging arm and is bracketed on either side by diglycine dipeptides acting as molecular universal joints. This structure provides a novel solution to the requirement that the cysteine-bound intermediates be able to access and orient themselves within the active sites of multiple partner enzymes. Adjacent to the swinging arm there is a conserved, deep, apolar pocket into which the beta-mercaptoethanol adduct extends. This pocket would be well suited to a role in protecting labile pathway intermediates from adventitious reactions.
authors.affiliation: Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom.
authors.forename: Véronique
authors.initials: V
authors.lastname: Sauvé
authors.forename: Stefano
authors.initials: S
authors.lastname: Bruno
authors.forename: Ben C
authors.initials: BC
authors.lastname: Berks
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Hemmings
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000502:physiology*; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000737:chemistry; D008623:Mercaptoethanol / Q000737:chemistry; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D050862:Oxidoreductases Acting on Sulfur Group Donors / Q000737:chemistry* / Q000502:physiology*; D042084:Paracoccus pantotrophus / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D013451:Sulfonic Acids / Q000737:chemistry; D013455:Sulfur / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D010455:Peptides; D013451:Sulfonic Acids; D008623:Mercaptoethanol; D013455:Sulfur; D050862:Oxidoreductases Acting on Sulfur Group Donors; C413329:SoxZ protein, Paracoccus pantotrophus; D003545:Cysteine