title: Characterization of a Gene Coding for the Complement System Component FB from Loxosceles laeta Spider Venom Glands.
abstract: The human complement system is composed of more than 30 proteins and many of these have conserved domains that allow tracing the phylogenetic evolution. The complement system seems to be initiated with the appearance of C3 and factor B (FB), the only components found in some protostomes and cnidarians, suggesting that the alternative pathway is the most ancient. Here, we present the characterization of an arachnid homologue of the human complement component FB from the spider Loxosceles laeta. This homologue, named Lox-FB, was identified from a total RNA L. laeta spider venom gland library and was amplified using RACE-PCR techniques and specific primers. Analysis of the deduced amino acid sequence and the domain structure showed significant similarity to the vertebrate and invertebrate FB/C2 family proteins. Lox-FB has a classical domain organization composed of a control complement protein domain (CCP), a von Willebrand Factor domain (vWFA), and a serine protease domain (SP). The amino acids involved in Mg2+ metal ion dependent adhesion site (MIDAS) found in the vWFA domain in the vertebrate C2/FB proteins are well conserved; however, the classic catalytic triad present in the serine protease domain is not conserved in Lox-FB. Similarity and phylogenetic analyses indicated that Lox-FB shares a major identity (43%) and has a close evolutionary relationship with the third isoform of FB-like protein (FB-3) from the jumping spider Hasarius adansoni belonging to the Family Salcitidae.
authors.affiliation: Immunochemistry Laboratory, Butantan Institute, São Paulo, Brazil.
authors.forename: Daniela Tiemi
authors.initials: DT
authors.lastname: Myamoto
authors.affiliation: Immunochemistry Laboratory, Butantan Institute, São Paulo, Brazil.
authors.forename: Giselle
authors.initials: G
authors.lastname: Pidde-Queiroz
authors.affiliation: Immunochemistry Laboratory, Butantan Institute, São Paulo, Brazil.
authors.forename: Rute Maria
authors.initials: RM
authors.lastname: Gonçalves-de-Andrade
authors.affiliation: Immunochemistry Laboratory, Butantan Institute, São Paulo, Brazil.
authors.forename: Aurélio
authors.initials: A
authors.lastname: Pedroso
authors.affiliation: Institute of Molecular and Experimental Medicine, School of Medicine, Cardiff University, Cardiff, United Kingdom.
authors.forename: Carmen W
authors.initials: CW
authors.lastname: van den Berg
authors.affiliation: Immunochemistry Laboratory, Butantan Institute, São Paulo, Brazil.
authors.forename: Denise V
authors.initials: DV
authors.lastname: Tambourgi
mesh_terms: D000818:Animals; D003176:Complement C3 / Q000235:genetics; D011415:Complement Factor B / Q000235:genetics* / Q000378:metabolism*; D010802:Phylogeny; D013111:Spider Venoms / Q000235:genetics*; D013112:Spiders / Q000145:classification / Q000235:genetics*
chemical_list: D003176:Complement C3; D013111:Spider Venoms; D011415:Complement Factor B