title: A perforin-like protein from a marine mollusk.
abstract: Abalone (gastropod mollusks) express a protein, abMpeg1, which is a homolog of two mammalian proteins that share homology with mammalian perforin, a cytolytic and immune-regulatory protein of lymphocytes. One of the mammalian proteins, Mpeg1, is expressed in mature macrophage and prion-infected mouse brains, while the other, Epcs50, is expressed in ectoplacental cone cells of the invading placenta. Although the functions of these three proteins remain unknown, their structural similarity to mammalian perforin suggests that they may be involved in cell killing, the inflammatory response or tissue invasion. Consistent with these proposed functions, the Mpeg1 gene family shows the signature of positive Darwinian selection (adaptive evolution). The perforin-homology domain of abMpeg1 contains the cytolytic "helix-turn-helix" domain of perforin, supporting the idea that abMpeg1 is a cytolytic protein of the abalone innate immune system. The alpha-helices of abMpeg1 are amphipathic as are those of perforin. The conservation among abMpeg1, mammalian Mpeg1, and Epcs50 shows that Mpeg1 proteins represent a novel, ancient protein family of probable immunological function.
authors.affiliation: Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0202, USA. sarmimah@yahoo.com
authors.forename: Silvia A
authors.initials: SA
authors.lastname: Mah
authors.forename: Gary W
authors.initials: GW
authors.lastname: Moy
authors.forename: Willie J
authors.initials: WJ
authors.lastname: Swanson
authors.forename: Victor D
authors.initials: VD
authors.lastname: Vacquier
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019143:Evolution, Molecular; D018628:Gene Dosage; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry; D051379:Mice; D008969:Molecular Sequence Data; D008974:Mollusca / Q000235:genetics / Q000378:metabolism*; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D017433:Protein Structure, Secondary; D012333:RNA, Messenger / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D008562:Membrane Glycoproteins; D008565:Membrane Proteins; C483884:Mpeg1 protein, mouse; C483885:Pfpl protein, mouse; D052899:Pore Forming Cytotoxic Proteins; D012333:RNA, Messenger; C483886:perforin, mouse; D054353:Perforin