title: Identification of unusual replacement of methionine by norleucine in recombinant interleukin-2 produced by E. coli.
abstract: Moderate amounts of norleucine incorporation into recombinant interleukin-2 (IL-2) produced in E. coli have been detected. Incorporation of norleucine occurs both at the amino terminal and internal methionines as confirmed by the isolation of norleucine-containing tryptic peptides which eluted later than the respective methionine-containing peptides by reverse-phase HPLC. The occurrence of norleucine in intact protein and modified peptides was determined by amino acid analysis and amino acid sequencing including Edman degradation and fast atom bombardment mass spectrometry. In the subsequent paper, we determined that norleucine incorporation is caused by the endogenous synthesis of norleucine in E. coli.
authors.affiliation: Amgen, Thousand Oaks, CA 91320.
authors.forename: H S
authors.initials: HS
authors.lastname: Lu
authors.forename: L B
authors.initials: LB
authors.lastname: Tsai
authors.forename: W C
authors.initials: WC
authors.lastname: Kenney
authors.forename: P H
authors.initials: PH
authors.lastname: Lai
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000614:Aminocaproates / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D004926:Escherichia coli / Q000378:metabolism*; D006801:Humans; D007376:Interleukin-2 / Q000032:analysis / Q000096:biosynthesis*; D013058:Mass Spectrometry; D008715:Methionine / Q000378:metabolism*; D008969:Molecular Sequence Data; D009646:Norleucine / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D011994:Recombinant Proteins / Q000032:analysis / Q000096:biosynthesis*; D014357:Trypsin / Q000378:metabolism
chemical_list: D000596:Amino Acids; D000614:Aminocaproates; D007376:Interleukin-2; D010446:Peptide Fragments; D011994:Recombinant Proteins; D009646:Norleucine; D008715:Methionine; D014357:Trypsin