RESUMEN
The ability of herbivorous beetles from the superfamilies Chrysomeloidea and Curculionoidea to degrade plant cell wall polysaccharides has only recently begun to be appreciated. The presence of plant cell wall degrading enzymes (PCWDEs) in the beetle's digestive tract makes this degradation possible. Sequences encoding these beetle-derived PCWDEs were originally identified from transcriptomes and strikingly resemble those of saprophytic and phytopathogenic microorganisms, raising questions about their origin; e.g. are they insect- or microorganism-derived? To demonstrate unambiguously that the genes encoding PCWDEs found in beetle transcriptomes are indeed of insect origin, we generated a bacterial artificial chromosome library from the genome of the leaf beetle Chrysomela tremula, containing 18 432 clones with an average size of 143 kb. After hybridizing this library with probes derived from 12 C. tremulaâ PCWDE-encoding genes and sequencing the positive clones, we demonstrated that the latter genes are encoded by the insect's genome and are surrounded by genes possessing orthologues in the genome of Tribolium castaneum as well as in three other beetle genomes. Our analyses showed that although the level of overall synteny between C. tremula and T. castaneum seems high, the degree of microsynteny between both species is relatively low, in contrast to the more closely related Colorado potato beetle.
Asunto(s)
Escarabajos/enzimología , Escarabajos/genética , Secuencia de Aminoácidos , Animales , Cromosomas Artificiales Bacterianos , Genoma , Genoma de los Insectos , Datos de Secuencia Molecular , Filogenia , Sintenía , TranscriptomaRESUMEN
During spliceosome assembly, splicing factor 1 (SF1) specifically recognizes the intron branch point sequence (BPS) UACUAAC in the pre-mRNA transcripts. We show that the KH-QUA2 region of SF1 defines an enlarged KH (hn RNP K) fold which is necessary and sufficient for BPS binding. The 3' part of the BPS (UAAC), including the conserved branch point adenosine (underlined), is specifically recognized in a hydrophobic cleft formed by the Gly-Pro-Arg-Gly motif and the variable loop of the KH domain. The QUA2 region recognizes the 5' nucleotides of the BPS (ACU). The branch point adenosine acting as the nucleophile in the first biochemical step of splicing is deeply buried. BPS RNA recognition suggests how SF1 may facilitate subsequent formation of the prespliceosomal complex A.
Asunto(s)
Proteínas de Unión al ADN , Intrones , Precursores del ARN/metabolismo , ARN Mensajero/metabolismo , Proteínas de Unión al ARN/química , Proteínas de Unión al ARN/metabolismo , Factores de Transcripción , Adenosina/química , Adenosina/metabolismo , Secuencias de Aminoácidos , Secuencia de Aminoácidos , Sitios de Unión , Humanos , Enlace de Hidrógeno , Interacciones Hidrofóbicas e Hidrofílicas , Modelos Moleculares , Datos de Secuencia Molecular , Mutación , Resonancia Magnética Nuclear Biomolecular , Conformación de Ácido Nucleico , Conformación Proteica , Pliegue de Proteína , Estructura Secundaria de Proteína , Estructura Terciaria de Proteína , Precursores del ARN/química , Factores de Empalme de ARN , ARN Mensajero/química , Proteínas de Unión al ARN/genética , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Empalmosomas/metabolismo , Uracilo/química , Uracilo/metabolismoRESUMEN
Cyclohexene nucleic acids (CeNA) were synthesized using classical phosporamidite chemistry. Incorporation of a cyclohexene nucleo-side in a DNA chain leads to an increase in stability of the DNA/RNA duplex. CeNA is stable against degradation in serum. A CeNA/RNA hybrid is able to activate E. Coli RNase H. resulting in cleavage of the RNA strand.
Asunto(s)
Ciclohexanos/química , Ácidos Nucleicos/química , ARN/química , Ribonucleasa H/metabolismo , Dicroismo Circular , Ciclohexanos/metabolismo , Ciclohexenos , ADN/química , Activación Enzimática , Escherichia coli/enzimología , Ácidos Nucleicos/metabolismo , ARN/metabolismo , Alcoholes del Azúcar/químicaRESUMEN
[reaction: see text]. An approach to the asymmetric intramolecular meta photocycloaddition of phenoxyalkenes is described. The beta-cyclodextrin complexes of several phenoxyalkenes have been synthesized and irradiated in the solid phase. The effect of the CD-hosting on the regio- and enantioselectivity is discussed. Values of ee up to 17% were obtained.
Asunto(s)
Alquenos/química , Ciclodextrinas/química , Fotoquímica/métodos , Cromatografía Líquida de Alta Presión , Espectroscopía de Resonancia Magnética , Modelos QuímicosRESUMEN
The synthesis of O-beta-D-ribofuranosyl-(1"-2')-adenosine-5"-O-phosphate and its suitably protected derivative for oligonucleotide synthesis have been developed.
Asunto(s)
Adenosina Monofosfato/química , Adenosina Monofosfato/análogos & derivados , Espectroscopía de Resonancia Magnética , Estructura MolecularRESUMEN
Small peptide fragments functionalized with dimelamine units spontaneously form well-defined assemblies. The hydrogen-bond donating and accepting sites in the peptide units are perfectly compatible with the hydrogen-bond assembly motif and slightly stabilize the assembly via additional hydrogen-bond formation.