title: Evolution of interleukin-18 binding proteins and interleukin-1 receptor, type II proteins.
abstract: Interleukin-18 (IL-18) is one of the pivotal cytokines controlling the defense mechanism called inflammation. As a first step to develop proteins for controlling the IL-18 level, we initiated a study of IL-18-binding proteins (IL-18BPs). Twenty-four IL-18BP family members, 11 from vertebrates and 13 from chordopoxviruses, were picked from the NCBI database. Eight of these vertebrate IL-18BPs and two of the chordopoxvirus IL18-BPs were identified here and characterized as new members of the IL-18BP family. Their IL-18 binding domains were aligned and the distribution of highly conserved critical amino acid residues was analyzed and used to construct a phylogenetic tree. From this tree it was inferred that at least two independent events created two different ancestral viral IL-18BP genes by retroposition of IL-18BP genes from the vertebrate lineage. These two events are estimated to have occurred after an ancient mammalian IL-18BP gene diverged from birds, and before the mammalian IL-18BP gene diverged into human, ungulate and rodent IL-18BP genes. Moreover, our results suggest that IL-18BP and interleukin-1 receptor, type II (IL-1R2) had a common ancestral gene and diverged from the ancestral gene into IL-18BP and IL-1R2 genes in the fish period.
authors.affiliation: Hirakata Ryoikuen, Hirakata, Osaka 573-0122, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Watanabe
authors.forename: Naohisa
authors.initials: N
authors.lastname: Goto
authors.forename: Yuko
authors.initials: Y
authors.lastname: Watanabe
authors.forename: Seiji
authors.initials: S
authors.lastname: Nishiguchi
authors.forename: Kazunori
authors.initials: K
authors.lastname: Shimada
authors.forename: Teruo
authors.initials: T
authors.lastname: Yasunga
authors.forename: Hiromichi
authors.initials: H
authors.lastname: Yamanishi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D019143:Evolution, Molecular; D006023:Glycoproteins / Q000235:genetics*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D017472:Receptors, Interleukin-1 / Q000235:genetics*; D053574:Receptors, Interleukin-1 Type II
chemical_list: D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; D017472:Receptors, Interleukin-1; D053574:Receptors, Interleukin-1 Type II; C118370:interleukin-18 binding protein