Human interleukin-5 expressed in Escherichia coli has N-terminal modifications.
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.
Rose
K
K
Département de Biochimie Médicale, Centre Médical Universitaire, Geneva, Switzerland.
Regamey
P O
PO
Anderegg
R
R
Wells
T N
TN
Proudfoot
A E
AE
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
D015848:Interleukin-5; D011994:Recombinant Proteins; D014357:Trypsin