RESUMO
Single-molecule methods have matured into central tools for studies in biology. Foerster resonance energy transfer (FRET) techniques, in particular, have been widely applied to study biomolecular structure and dynamics. The major bottleneck for a facile and general application of these studies arises from the need to label biological samples site-specifically with suitable fluorescent dyes. In this work, we present an optimized strategy combining click chemistry and the genetic encoding of unnatural amino acids (UAAs) to overcome this limitation for proteins. We performed a systematic study with a variety of clickable UAAs and explored their potential for high-resolution single-molecule FRET (smFRET). We determined all parameters that are essential for successful single-molecule studies, such as accessibility of the probes, expression yield of proteins, and quantitative labeling. Our multiparameter fluorescence analysis allowed us to gain new insights into the effects and photophysical properties of fluorescent dyes linked to various UAAs for smFRET measurements. This led us to determine that, from the extended tool set that we now present, genetically encoding propargyllysine has major advantages for state-of-the-art measurements compared to other UAAs. Using this optimized system, we present a biocompatible one-step dual-labeling strategy of the regulatory protein RanBP3 with full labeling position freedom. Our technique allowed us then to determine that the region encompassing two FxFG repeat sequences adopts a disordered but collapsed state. RanBP3 serves here as a prototypical protein that, due to its multiple cysteines, size, and partially disordered structure, is not readily accessible to any of the typical structure determination techniques such as smFRET, NMR, and X-ray crystallography.
Assuntos
Fluorescência , Proteínas/química , Aminoácidos/química , Química Click , Transferência Ressonante de Energia de Fluorescência , Modelos Moleculares , Estrutura Molecular , Engenharia de Proteínas , Proteínas/genética , Proteínas/isolamento & purificaçãoRESUMO
Ligands from the naltrexamine series have consistently demonstrated agonist activity at kappa opioid receptors (KOR), with varying activity at the mu opioid receptor (MOR). Various 6 beta-cinnamoylamino derivatives were made with the aim of generating ligands with a KOR agonist/MOR partial agonist profile, as ligands with this activity may be of interest as treatment agents for cocaine abuse. The ligands all displayed the desired high affinity, nonselective binding in vitro and in the functional assays were high efficacy KOR agonists with some partial agonist activity at MOR. Two of the new ligands (12a, 12b) have been evaluated in vivo, with 12a acting as a KOR agonist and therefore somewhat similar to the previously evaluated analogues 3-6, while 12b displayed predominant MOR agonist activity.
Assuntos
Naltrexona/análogos & derivados , Receptores Opioides kappa/agonistas , Receptores Opioides mu/agonistas , Animais , Células CHO , Cricetinae , Cricetulus , Naltrexona/farmacologia , Ratos , Espectrometria de Massas por Ionização por ElectrosprayRESUMO
A new series of ligands has been synthesized where the cinnamoyl group of the 14-cinnamoylamino morphinones has been introduced to the 7alpha-substituent of the 6,14-bridged oripavine series. In vitro the compounds were mostly low efficacy partial agonists or antagonists with some selectivity for the mu opioid receptor, with evidence of micro efficacy in vivo. The similarity in SAR between these 6,14-bridged oripavines and the 14-cinnamoylamino series suggests a similar mode of interaction with the micro opioid receptor.
