Properties of a human alpha-interferon purified from E. coli extracts.
A human alpha interferon, designated HuIFN-alpha A, produced in E. coli by direct expression of cloned cDNA [Goeddel et al., Nature 287, 411--416 (1980)] has been purified from bacterial extracts and characterized. The protein has a molecular weight (19,400 by SDS/PAGE) and amino acid composition consistent with the DNA sequence. The pI was determined to be 6.1. The molecule has a specific activity of 1.5 x 10(8) NIH reference units/mg of protein. The sequence of the first 35 amino acids is identical to that expected from the nucleotide sequence. About 50% of the molecules begin with the expected cysteine, and 50% begin with the initiator methionine which E. coli apparently did not remove efficiently. Analysis of a trypsin digest of the native molecule showed that all four of the molecule's cysteines are involved in disulfide bonds: Cys1 is bonded to Cys98, and Cys29 is bonded to Cys 138.
D000596:Amino Acids / Q000032:analysis; D002851:Chromatography, High Pressure Liquid; D003001:Cloning, Molecular; D004220:Disulfides; D004926:Escherichia coli; D006801:Humans; D007372:Interferons / Q000235:genetics / Q000302:isolation & purification*; D007526:Isoelectric Point; D007962:Leukocytes; D008970:Molecular Weight; D010446:Peptide Fragments / Q000032:analysis
D000596:Amino Acids; D004220:Disulfides; D010446:Peptide Fragments; D007372:Interferons