title: Human interleukin-5 expressed in Escherichia coli has N-terminal modifications.
abstract: Recombinant human interleukin-5 exists as four major isoforms all possessing N-terminal methionine. Peptide mapping and subsequent analysis by fast-atom-bombardment mass spectrometry (f.a.b.-m.s.) have shown that N-terminal modifications are the cause of the charge heterogeneity. In order of decreasing abundance, these are unmodified methionine, retention of N-terminal formyl group, oxidation of N-terminal methionine to sulphoxide and carbamoylation of the N-terminus. These results were confirmed by analysis of the reduced and alkylated intact protein by electrospray-ionization mass spectrometry. The implications of these findings for the production and characterization of recombinant proteins are briefly discussed.
authors.affiliation: Département de Biochimie Médicale, Centre Médical Universitaire, Geneva, Switzerland.
authors.forename: K
authors.initials: K
authors.lastname: Rose
authors.forename: P O
authors.initials: PO
authors.lastname: Regamey
authors.forename: R
authors.initials: R
authors.lastname: Anderegg
authors.forename: T N
authors.initials: TN
authors.lastname: Wells
authors.forename: A E
authors.initials: AE
authors.lastname: Proudfoot
mesh_terms: D002851:Chromatography, High Pressure Liquid; D003001:Cloning, Molecular; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli; D006801:Humans; D015848:Interleukin-5 / Q000737:chemistry* / Q000235:genetics; D007525:Isoelectric Focusing; D010449:Peptide Mapping; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D016339:Spectrometry, Mass, Fast Atom Bombardment; D014357:Trypsin
chemical_list: D015848:Interleukin-5; D011994:Recombinant Proteins; D014357:Trypsin