RESUMO
Interleukin 1 receptor antagonist (IL-1ra) is a protein that binds to the IL-1 receptor and blocks the binding of both IL-1 alpha and -beta without inducing a signal of its own. Human IL-1ra has some sequence identity to human IL-1 beta, but the evolutionary relationship between these proteins has been unclear. We show that the genes for human, mouse, and rat IL-1ra are similar to the genes for IL-1 alpha and IL-1 beta in intron-exon organization, indicating that gene duplication events were important in the creation of this gene family. Furthermore, an analysis of sequence comparisons and mutation rates for IL-1 alpha, IL-1 beta, and IL-1ra suggests that the duplication giving rise to the IL-1ra gene was an early event in the evolution of the gene family. Comparisons between the mature sequences for IL-1ra, IL-1 alpha, and IL-1 beta suggest that IL-1ra has a beta-stranded structure like to IL-1 alpha and IL-1 beta, consistent with the three proteins being related. The N-terminal sequences of IL-1ra appear to be derived from a region of the genome different than those of IL-1 alpha and IL-1 beta, thus explaining their different modes of biosynthesis and suggesting an explanation for their different biological activities.
Assuntos
Interleucina-1/genética , Família Multigênica , Receptores Imunológicos/antagonistas & inibidores , Sequência de Aminoácidos , Animais , Sequência de Bases , Humanos , Interleucina-1/metabolismo , Íntrons , Camundongos , Dados de Sequência Molecular , Mutação , Ratos , Ratos Endogâmicos , Receptores de Interleucina-1 , Alinhamento de Sequência , Homologia de Sequência do Ácido NucleicoRESUMO
Secretory leukocyte protease inhibitor (SLPI) is a two-domain protein that inhibits a wide range of proteases including chymotrypsin, leukocyte elastase, and trypsin. Based on its homology to other protease inhibitors and on x-ray crystallography of an SLPI-chymotrypsin complex it has been proposed that the elastase and chymotrypsin-inhibitory site is in the COOH-terminal domain and that the trypsin-inhibitory site is in the NH2-terminal domain. We have prepared muteins of SLPI by site-directed mutagenesis of a synthetic gene for the protein, followed by expression in Escherichia coli. The protease-inhibitory activities of these muteins indicate that leucine 72 in the COOH-terminal domain is at the inhibitory site for elastase and chymotrypsin. Unexpectedly, our measurements indicate that the trypsin-inhibitory site is not in the NH2-terminal domain. Instead they suggest that leucine 72 is also the inhibitory site for trypsin, even though the amino acid residues at the inhibitory sites of other trypsin inhibitors are almost always either lysine or arginine.
Assuntos
Inibidores de Proteases , Proteínas , Inibidores de Serina Proteinase/farmacologia , Sequência de Aminoácidos , Sequência de Bases , Sítios de Ligação , Cromatografia Líquida de Alta Pressão , Quimotripsina/antagonistas & inibidores , Escherichia coli/genética , Regulação da Expressão Gênica , Humanos , Leucina , Dados de Sequência Molecular , Mutação , Elastase Pancreática/antagonistas & inibidores , Pepsina A/metabolismo , Conformação Proteica , Proteínas Secretadas Inibidoras de Proteinases , Proteínas Recombinantes/farmacologia , Inibidor Secretado de Peptidases Leucocitárias , Inibidores de Serina Proteinase/genética , Transcrição Gênica , Inibidores da TripsinaRESUMO
Three interleukin-1 inhibitors have been purified to homogeneity from medium conditioned by human monocytes. Partial sequence analysis and digestion with N-glycanase indicate that these are glycosylation forms of a single protein. The protein binds to the interleukin-1 receptor but has no interleukin-1-like activity, even at very high concentrations, and is therefore a pure receptor antagonist.