title: The 31-kDa precursor of interleukin 1 alpha is myristoylated on specific lysines within the 16-kDa N-terminal propiece.
abstract: The cytokine interleukin 1 alpha (IL-1 alpha) is a critical mediator of the immune and inflammatory responses. A unique determinant of its activity as compared with IL-1 beta may be its association with the plasma membrane. While the biologic activity of "membrane IL-1" has been extensively reported, the mechanism of membrane binding remains unclear. We report that the N terminus of the 31-kDa IL-1 alpha precursor is myristoylated on specific internal lysine residues. Immunoprecipitation of [3H]myristic acid-radiolabeled human monocyte lysates with IgG antibodies to the 31-kDa IL-1 alpha precursor recovered a protein with the physicochemical properties of the IL-1 alpha N-terminal propiece (16 kDa, pI 4.45). Glycyl N-myristoylation of this protein is precluded by the absence of a glycine residue at position 2, suggesting that the propiece is myristoylated on epsilon-amino groups of lysine. To determine which lysine(s) are acylated, a series of synthetic peptides containing all lysines found in the IL-1 alpha N-terminal propiece were used in an in vitro myristoylation assay containing peptide, myristoyl-CoA, and monocyte lysate as enzyme source. Analysis of the reaction products by reverse-phase HPLC and gas-phase sequencing demonstrated the specific myristoylation of Lys-82 and Lys-83, yielding predominantly monoacylated product. A conserved sequence in the IL-1 beta propiece was myristoylated with at least 8-fold less efficiency. Acylation of the IL-1 alpha precursor by a previously unrecognized lysyl epsilon-amino N-myristoyl-transferase activity may facilitate its specific membrane targeting.
authors.affiliation: Medical Service, San Francisco Veterans Administration Medical Center, CA 94121.
authors.forename: F T
authors.initials: FT
authors.lastname: Stevenson
authors.forename: S L
authors.initials: SL
authors.lastname: Bursten
authors.forename: C
authors.initials: C
authors.lastname: Fanton
authors.forename: R M
authors.initials: RM
authors.lastname: Locksley
authors.forename: D H
authors.initials: DH
authors.lastname: Lovett
mesh_terms: D000215:Acylation; D000595:Amino Acid Sequence; D002478:Cells, Cultured; D006801:Humans; D066298:In Vitro Techniques; D007375:Interleukin-1 / Q000737:chemistry / Q000378:metabolism*; D008239:Lysine / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009226:Myristates / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D011498:Protein Precursors / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D007375:Interleukin-1; D009226:Myristates; D010455:Peptides; D011498:Protein Precursors; D008239:Lysine