title: Two novel defensin-encoding genes of the Chagas disease vector Triatoma brasiliensis (Reduviidae, Triatominae): gene expression and peptide-structure modeling.
abstract: Defensins are cysteine-rich peptides involved in the innate immunity of insects and many other organisms. In the present study, two novel defensin-encoding cDNAs and the respective genomic DNAs (def3 and def4) of Triatoma brasiliensis were identified and their tissue-specific and temporal expression was characterized. Both of the deduced mature peptides consisted of 43 amino acid residues and were highly similar to previously identified triatomine defensins (81.4-100%). Semi-quantitative RT-PCR data showed that def3 was constitutively expressed in the fat body and was induced in salivary glands and the small intestine at 5 and 3 days after feeding (daf), respectively. The def4 mRNA level was highly up-regulated in the stomach and fat-body tissues at 5 and 3 daf, respectively. The three-dimensional structures of these defensins were predicted using a homology modeling approach with Def-AAA, the defensin from Anopheles gambiae, as template (62-74% identity). A map of the electrostatic potential of these models revealed that, despite their similar folding patterns, mature Def2 and Def4 have a more cationic structure than is the case for Def1 and Def3. Such differences may orient the antimicrobial profile of these defensins against distinct targets in different organs of the insect.
authors.affiliation: Laboratório de Biologia de Tripanosomatídeos, Instituto Oswaldo Cruz-IOC/FIOCRUZ, Av. Brasil 4365, Zip Code: 21045-900, Rio de Janeiro, Brazil. peter.waniek@cityweb.de
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Waniek
authors.forename: Helena C
authors.initials: HC
authors.lastname: Castro
authors.forename: Plínio C
authors.initials: PC
authors.lastname: Sathler
authors.forename: Leonardo
authors.initials: L
authors.lastname: Miceli
authors.forename: Ana M
authors.initials: AM
authors.lastname: Jansen
authors.forename: Catarina A C
authors.initials: CA
authors.lastname: Araújo
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D014355:Chagas Disease / Q000469:parasitology*; D023082:Defensins / Q000096:biosynthesis*; D005786:Gene Expression Regulation; D019476:Insect Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D007303:Insect Vectors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D010802:Phylogeny; D011485:Protein Binding; D020064:Reduviidae / Q000737:chemistry / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D023082:Defensins; D019476:Insect Proteins