RESUMO
Juvenile hormones (JHs) play key roles in regulating metamorphosis and reproduction in insects. The last two steps of JH synthesis diverge depending on the insect order. In Lepidoptera, epoxidation by a P450 monooxygenase precedes esterification by a juvenile hormone acid methyltransferase (JHAMT). In Orthoptera, Dictyoptera, Coleoptera and Diptera epoxidation follows methylation. The aim of our study was to gain insight into the structural basis of JHAMT's substrate recognition as a means to understand the divergence of these pathways. Homology modeling was used to build the structure of Aedes aegypti JHAMT. The substrate binding site was identified, as well as the residues that interact with the methyl donor (S-adenosylmethionine) and the carboxylic acid of the substrate methyl acceptors, farnesoic acid (FA) and juvenile hormone acid (JHA). To gain further insight we generated the structures of Anopheles gambiae, Bombyx mori, Drosophila melanogaster and Tribolium castaneum JHAMTs. The modeling results were compared with previous experimental studies using recombinant proteins, whole insects, corpora allata or tissue extracts. The computational study helps explain the selectivity toward the (10R)-JHA isomer and the reduced activity for palmitic and lauric acids. The analysis of our results supports the hypothesis that all insect JHAMTs are able to recognize both FA and JHA as substrates. Therefore, the order of the methylation/epoxidation reactions may be primarily imposed by the epoxidase's substrate specificity. In Lepidoptera, epoxidase might have higher affinity than JHAMT for FA, so epoxidation precedes methylation, while in most other insects there is no epoxidation of FA, but esterification of FA to form MF, followed by epoxidation to JH III.
Assuntos
Aedes/enzimologia , Proteínas de Insetos/química , Proteínas de Insetos/metabolismo , Hormônios Juvenis/biossíntese , Metiltransferases/química , Metiltransferases/metabolismo , Aedes/química , Aedes/genética , Aedes/metabolismo , Sequência de Aminoácidos , Animais , Sítios de Ligação , Ácidos Graxos Insaturados/metabolismo , Proteínas de Insetos/genética , Insetos/química , Insetos/enzimologia , Insetos/genética , Isomerismo , Hormônios Juvenis/química , Metiltransferases/genética , Modelos Moleculares , Dados de Sequência Molecular , Processamento de Proteína Pós-Traducional , Alinhamento de Sequência , Especificidade por SubstratoRESUMO
Autogeny, the capacity of a female to lay eggs without having ingested any blood meal in the adult stage, was studied in three species of Triatominae: Triatoma infestans, Triatoma rubrovaria, and Rhodnius prolixus. When nymphs of T. rubrovaria and R. prolixus were fed chicken blood, autogeny occurred frequently, even with only one meal. In T. infestans autogeny was frequent as well, but demanded at least two nymphal blood meals. Total number of autogenic eggs was positively correlated with the body weight of the adult female. We conclude, therefore, that autogeny is common in Triatominae.
Assuntos
Oviposição , Rhodnius/fisiologia , Triatoma/fisiologia , Animais , Feminino , Masculino , Comportamento Sexual AnimalRESUMO
When 3H-20-hydroxyecdysone was injected into Triatoma infestans during the fifth nymphal instar, it was converted to very polar metabolites (peak 1). The polar metabolites were glucuronoconjugates of 20-hydroxyecdysone. Acetylation of the conjugates followed by hydrolysis with glucuronidase gave a major labelled product: 20-hydroxyecdysone and minor peaks corresponding to a mixture of 20-hydroxyecdysone acetates. These results indicated that the 2,3,22,25-glucuronoconjugates of 20-hydroxyecdysone were the principal products in the inactivation process.
Assuntos
Ecdisterona/metabolismo , Glucuronidase/metabolismo , Triatoma/metabolismo , Triatominae/metabolismo , Acetilação , Animais , Cromatografia em Camada Fina , Ecdisterona/biossíntese , TrítioRESUMO
When 3H-20-hydroxyecdysone was injected into Triatoma infestans during the fifth nymphal instar, it was converted to very polar metabolites (peak 1). The polar metabolites were glucuronoconjugates of 20-hydroxyecdysone. Acetylation of the conjugates followed by hydrolysis with glucuronidase gave a major labelled product: 20-hydroxyecdysone and minor peaks corresponding to a mixture of 20-hydroxyecdysone acetates. These results indicated that the 2,3,22,25-glucuronoconjugates of 20-hydroxyecdysone were the principal products in the inactivation process.
RESUMO
Al inyectar 20-OH-ecdisona-3H en el 5o.estadio ninfal de T. infestans, se observo la transformacion de la misma a metabolitos muy polares (pico I). La mayor parte de los constituyentes del pico I evidenciaron ser glucurono-conjugados al ser analizados por hidrolisis enzimaticas. La acetilacion de los conjugados seguida por hidrolisis enzimatica permitio identificar las posiciones ocupadas por el acido glucuronico al inactivar la 20-OH-ecdisona.Al inyectar los conjutados radiactivos aislados (pico I) en ninfas del 5o. estadio, se observo que no se revierte el proceso de inactivacion
Assuntos
Animais , Cromatografia em Gel , Ecdisona , TriatomaRESUMO
Al inyectar 20-OH-ecdisona-3H en el 5o.estadio ninfal de T. infestans, se observo la transformacion de la misma a metabolitos muy polares (pico I). La mayor parte de los constituyentes del pico I evidenciaron ser glucurono-conjugados al ser analizados por hidrolisis enzimaticas. La acetilacion de los conjugados seguida por hidrolisis enzimatica permitio identificar las posiciones ocupadas por el acido glucuronico al inactivar la 20-OH-ecdisona.Al inyectar los conjutados radiactivos aislados (pico I) en ninfas del 5o. estadio, se observo que no se revierte el proceso de inactivacion