RESUMO
T4 lysozyme was thought to destroy bacteria by its muramidase activity. However, we demonstrate here that amphipathic helix stretches in the C-terminus of T4 lysozyme mediate its bactericidal and fungistatic activities. In heat-denatured T4 lysozyme, the enzymatic activity is completely abolished but unexpectedly, the antimicrobial functions remain preserved. Small synthetic peptides corresponding to amphipathic C-terminal domains of T4 lysozyme show a microbicidal activity. Its membrane disturbing activity was directly demonstrated for bacterial, fungal and plant cells but not in a hemolysis assay. Comparable results were obtained with hen egg white lysozyme. This opens up many new opportunities for optimization of lysozymes as antimicrobial agents in various applications by protein engineering.
Assuntos
Anti-Infecciosos/farmacologia , Bacteriófago T4/enzimologia , Muramidase/farmacologia , Animais , Antibacterianos , Anti-Infecciosos/metabolismo , Membrana Celular/efeitos dos fármacos , Quitinases/metabolismo , Clara de Ovo , Escherichia coli/efeitos dos fármacos , Escherichia coli/fisiologia , Muramidase/genética , Muramidase/metabolismo , Mutagênese , Peptídeos , Phytophthora/efeitos dos fármacos , Phytophthora/crescimento & desenvolvimento , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Proteínas Recombinantes de Fusão/farmacologiaRESUMO
Phytophthora infestans is the most important fungal pathogen in the cultivated potato (Solanum tuberosum). Dominant, race-specific resistance alleles and quantitative resistance--the latter being more important for potato breeding--are found in the germplasm of cultivated and wild potato species. Quantitative trait loci (QTLs) for resistance to two races of P. infestans have been mapped in an F1 progeny of a cross between non-inbred diploid potato parents with multiple alleles. Interval mapping methods based on highly informative restriction fragment length polymorphism markers revealed 11 chromosome segments on 9 potato chromosomes showing significant contrasts between marker genotypic classes. Whereas phenotypically no difference in quantitative resistance response was observed between the two fungal races, QTL mapping identified at least one race specific QT locus. Two QT regions coincided with two small segments on chromosomes V and XII to which the dominant alleles R1, conferring race specific resistance to P. infestans, Rx1 and Rx2, both inducing extreme resistance to potato virus X, have been allocated in independent mapping experiments. Some minor QTLs were correlated with genetic loci for specific proteins related to pathogenesis, the expression of which is induced after infection with P. infestans.
Assuntos
Mapeamento Cromossômico , Genes de Plantas , Phytophthora/fisiologia , Solanum tuberosum/genética , Solanum tuberosum/imunologia , Alelos , Análise de Variância , Cruzamentos Genéticos , Genótipo , Fenótipo , Doenças das Plantas/genética , Polimorfismo de Fragmento de Restrição , Solanum tuberosum/microbiologiaRESUMO
Late blight in potato is caused by the fungus Phytophthora infestans and can inflict severe damage on the potato crop. Resistance to P. infestans is either based on major dominant R genes conferring vertical, race-specific resistance or on "minor" genes inducing horizontal, unspecific resistance. A dihaploid potato line was identified which carried the R1 gene, conferring vertical resistance to all P. infestans races, with the exception of those homozygous for the recessive virulence allele of the locus V1. The F1 progeny of a cross between this resistant parent P(R1) and P(r), a line susceptible to all races, was analysed for segregation of R1 and of restriction fragment length polymorphism (RFLP) markers distributed on the potato RFLP map comprising more than 300 loci. The R1 locus was mapped to chromosome V in the interval between RFLP markers GP21 and GP179. The map position of R1 was found to be very similar to the one of Rx2, a dominant locus inducing extreme resistance to potato virus X.
