Identification of nine interferon-alpha subtypes produced by Sendai virus-induced human peripheral blood leucocytes.
The human interferon-alpha (IFN-alpha) family is encoded by 13 different functional genes, and including all cloned sequence variants there are 28 potential IFN-alpha proteins. To find out which of the described sequences are expressed in normal human leucocytes, we have isolated and partly characterized the components of a highly purified IFN-alpha preparation produced by Sendai virus-induced human peripheral blood leucocytes. The identification protocol consisted of N-terminal sequencing and mass mapping of the proteins separated by reverse-phase HPLC and/or SDS/PAGE. The highly purified leucocyte IFN-alpha preparation was found to contain at least nine different IFN-alpha species: IFN-alpha1a, IFN-alpha2b, IFN-alpha4b, IFN-alpha7a, IFN-alpha8b, IFN-alpha10a, IFN-alpha14c, IFN-alpha17b and IFN-alpha21b. IFN-alpha1a was the major subtype, comprising approx. 30% of total leucocyte IFN-alpha. IFN-alpha14c, the only subtype containing potential N-glycosylation sites, was shown to be glycosylated at Asn-72. Molecular mass determination of the intact proteins by electrospray ionization MS showed that there are no other post-translational modifications in the IFN-alpha subtypes than the glycosylation of IFN-alpha2b and IFN-alpha14c. Only one sequence variant was found for each subtype, suggesting that the other described gene sequences represent allelic variants or mutations that are more rarely found in the general population.
Nyman
T A
TA
Institute of Biotechnology, Protein Chemistry Laboratory, P.O. Box 56 (Viikinkaari 9), FIN-00014 University of Helsinki, Finland.
Tölö
H
H
Parkkinen
J
J
Kalkkinen
N
N
D000595:Amino Acid Sequence; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D016898:Interferon-alpha / Q000096:biosynthesis / Q000737:chemistry / Q000145:classification* / Q000302:isolation & purification; D007962:Leukocytes / Q000378:metabolism*; D008969:Molecular Sequence Data; D018108:Respirovirus / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D016898:Interferon-alpha