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Master's Dissertation
DOI
10.11606/D.87.2013.tde-14052014-165128
Document
Author
Full name
Poliana Garcia Corrêa
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2013
Supervisor
Committee
Oguiura, Nancy (President)
Silva Junior, Pedro Ismael da
Silva, Alvaro Rossan de Brandão Prieto da
Title in Portuguese
Prospecção gênica e atividade antimicrobiana de b-defensina-símiles em viperídeos.
Keywords in Portuguese
Agentes antimicrobianos
Evolução molecular
Filogênia
Imunidade natural
Polimorfismo
Viperidae
Abstract in Portuguese
As b-defensinas são pequenos peptídeos catiônicos com estrutura rica em folhas b pregueadas e seis cisteínas conservadas. São bastante estudadas em mamíferos, mas pouco em serpentes. Utilizando a PCR foram descritos 13 genes b-defensina-símiles em serpentes do gênero Bothrops e Lachesis . Eles se organizam em três éxons e dois íntrons; há alta similaridade no éxon1, íntron 1 e 2, mas os éxons 2 e 3 estão sob evolução acelerada. A análise filogenética por máxima parcimônia revelou que o gene ancestral de b-defensina-símile pode ter três éxons em vertebrados e sua evolução ocorreu de acordo com o modelo de nascimento-e-morte. Peptídeos b-defensina-símiles reduzidos, testados por ensaio de inibição de crescimento em meio líquido, apresentaram atividade inibitória contra Escherichia coli, Citrobacter freundii, Micrococcus luteus e Staphylococcus aureus. A crotamina reduzida foi mais ativa que a forma nativa. Os resultados indicam que a carga líquida era a característica bioquímica mais importante na atividade antibiótica dos peptídeos b-defensina-símiles.
Title in English
Gene survey and antimicrobial activity of beta-defensin-like in viperid.
Keywords in English
Antimicrobial agents
Molecular evolution
Natural immunity
Phylogeny
Polymorphism
Viperidae
Abstract in English
b-defensins are small basic cationic peptides with b-sheet-rich fold plus six conserved cysteines. They are fully studied in mammals, but scarce in snakes. Using a PCR approach, we described 13 b-defensin-like sequences in Bothrops and Lachesis snakes. They are organized in three exons and two introns; they show high similarities in exon 1, intron 1 and intron 2, but exons 2 and 3 have undergone accelerated evolution. Phylogenetic analysis was done using maximum parsimony indicate that the ancestral b-defensin-like gene may have three exons in vertebrates and that their evolution occurred according to a birth-and-death model. Reduced b-defensin-like peptides were tested by microbroth dilution assay, showed inhibitory activity against Escherichia coli, Citrobacter freundii, Micrococcus luteus e Staphylococcus aureus. The reduced form of crotamine was more active than native. The results indicate that the positive net charge is the most important biochemical characteristic of b-defensin-like peptides to antibiotic activity.
 
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Publishing Date
2014-05-21
 
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