title: The complete amino acid sequence confirms the presence of pseudoazurin in Thiosphaera pantotropha.
abstract: The complete amino acid sequence, obtained by direct protein sequencing, of the pseudoazurin from Thiosphaera pantotropha is reported. It shows sequence identities varying from 46 to 66% with previously sequenced pseudoazurins. Previously identified conserved residues with key functions in pseudoazurins are found in the protein from T. pantotropha with the exception of glycine-39, the carbonyl group of which has been considered as a ligand to the copper, which is replaced by a serine residue. Electrospray-ionization MS (ESI-MS) has shown that pseudoazurin from T. pantotropha often contains two polypeptide species differing in molecular mass by 16 Da, presumably owing to oxidation of a methionine residue to a sulphoxide derivative. These two species have different endoproteinase Arg-C digestion patterns. Conditions for ESI-MS were identified that permitted either the retention or the loss of the single copper ion associated with the pseudoazurin. The aberrant tendency of T. pantotropha pseudoazurin to form a disulphide-bridged dimer on SDS/PAGE under some conditions is described.
authors.affiliation: Department of Biochemistry, University of Oxford, U.K.
authors.forename: C
authors.initials: C
authors.lastname: Chan
authors.forename: A C
authors.initials: AC
authors.lastname: Willis
authors.forename: C V
authors.initials: CV
authors.lastname: Robinson
authors.forename: R T
authors.initials: RT
authors.lastname: Aplin
authors.forename: S E
authors.initials: SE
authors.lastname: Radford
authors.forename: S J
authors.initials: SJ
authors.lastname: Ferguson
mesh_terms: D000595:Amino Acid Sequence; D001400:Azurin / Q000031:analogs & derivatives* / Q000737:chemistry; D001483:Base Sequence; D002942:Circular Dichroism; D008401:Gas Chromatography-Mass Spectrometry; D006090:Gram-Negative Bacteria / Q000737:chemistry*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: C047163:pseudoazurin; D001400:Azurin