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cDNA Sequence Coding for the α’‐Chain of the Third Complement Component in the African Lungfish
Author(s) -
Akie Sato,
Holger Sültmann,
Mayer We,
Felipe Figueroa,
Herbert Tichy,
Jörg Klein
Publication year - 1999
Publication title -
scandinavian journal of immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.934
H-Index - 88
eISSN - 1365-3083
pISSN - 0300-9475
DOI - 10.1046/j.1365-3083.1999.00512.x
Subject(s) - lungfish , biology , complementary dna , coding region , peptide sequence , genetics , complement factor b , conserved sequence , complement factor i , vertebrate , immunoglobulin light chain , phylogenetic tree , evolutionary biology , complement system , gene , antibody , fishery , fish <actinopterygii>
cDNA clones coding for almost the entire C3 α‐chain of the African lungfish ( Protopterus aethiopicus ), a representative of the Sarcopterygii (lobe‐finned fishes), were sequenced and characterized. From the sequence it is deduced that the lungfish C3 molecule is probably a disulphide‐bonded α:β dimer similar to that of the C3 components of other jawed vertebrates. The deduced sequence contains conserved sites presumably recognized by proteolytic enzymes (e.g. factor I) involved in the activation and inactivation of the component. It also contains the conserved thioester region and the putative site for binding properdin. However, the site for the interaction with complement receptor 2 and factor H are poorly conserved. Either complement receptor 2 and factor H are not present in the lungfish or they bind to different residues at the same or a different site than mammalian complement receptor 2 and factor H. The C3 α‐chain sequences faithfully reflect the phylogenetic relationships among vertebrate classes and can therefore be used to help to resolve the long‐standing controversy concerning the origin of the tetrapods.