C6-Like and C3-Like Molecules from the Cephalochordate, Amphioxus, Suggest a Cytolytic Complement System in Invertebrates |
| |
Authors: | Miho M Suzuki Nori Satoh Masaru Nonaka |
| |
Institution: | (1) Department of Zoology, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan, JP;(2) Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo, Tokyo 113-0033, Japan, JP |
| |
Abstract: | The mammalian immune system has cytotoxic mechanisms, both cellular and humoral, that destroy the membrane integrity of target
cells. The main effector molecules of these cytolytic mechanisms—perforin, used by killer lymphocytes, and the membrane attack
complex (MAC) components of the complement system—share a unique module called the MAC/perforin module. Until now, both immunological
cytotoxicity and the MAC/perforin module have been reported only in jawed vertebrates. Here, we report the identification
of a protein containing the MAC/perforin module from the invertebrate cephalochordate, amphioxus (Branchiostoma belcheri), using expressed sequence tag (EST) analysis of the notochord. The deduced amino acid sequence of this molecule is most
similar to the primary structure of human complement component C6 and is designated AmphiC6. AmphiC6 shares a unique modular
structure, including the MAC/perforin module, with human C6 and other MAC components. Another EST clone predicts the presence
of a thioester-containing protein with the closest structural similarity to vertebrate C3 (therefore designated AmphiC3).
AmphiC3 retains most of the functionally important residues of vertebrate C3 and is shown by phylogenetic analysis to be derived
directly from the common ancestor of vertebrate C3, C4, and C5. Only opsonic activity has been assigned to the invertebrate
complement system until now. Therefore, this is the first molecular evidence for complement-mediated immunological cytotoxicity
in invertebrates.
Received: 24 August 2001 / Accepted: 12 November 2001 |
| |
Keywords: | : Immunological cytotoxicity — Modular structure — Complement — Amphioxus — Membrane attack complex |
本文献已被 PubMed SpringerLink 等数据库收录! |
|