Synthesis of a bis-azido analogue of acromelic acid for radioisotope-free photoaffinity labeling and biochemical studies

Yucasin DF, a potent and persistent inhibitor of auxin biosynthesis in plants

The plant hormone auxin plays a crucial role in plant growth and development. Indole-3-acetic acid (IAA), a natural auxin, is mainly biosynthesized by two sequential enzyme reactions catalyzed by TAA1 and YUCCA (YUC). TAA1 is involved in the conversion of tryptophan to IPA, and YUC catalyzes the conversion of IPA to IAA. We previously demonstrated that yucasin inhibits AtYUC1 enzyme activity and suppress high-auxin phenotype of YUC overexpression plants, although yucasin displayed weak effects on the auxin-related phenotype of wild-type plants. To develop more potent YUC inhibitors, various derivatives of yucasin were synthesized, and their structure–activity relationships were investigated. Yucasin difluorinated analog (YDF) (5-[2,6-difluorophenyl]-2,4-dihydro-[1,2,4]-triazole-3-thione) was identified to be a more potent YUC inhibitor than the original yucasin. YDF caused an auxin-deficient phenotype in Arabidopsis wild-type plants that was restored with auxin application. YDF was found to be highly stable regarding metabolic conversion in vivo, accounting for the potent activity of the inhibition of IAA biosynthesis in planta. Photoaffinity labeling experiments demonstrated that yucasin-type inhibitors bind to the active site of AtYUC1. YDF is a promising auxin biosynthesis inhibitor and is a useful chemical tool for plant biology and agrochemical studies.

Tandem photoaffinity labeling-bioorthogonal conjugation in medicinal chemistry

Photoaffinity labeling has a longstanding history as a powerful biochemical technique. However, photoaffinity labeling has significantly evolved over the past decade principally due to its coupling with bioorthogonal/click chemistry reactions. This review aims to highlight tandem photoaffinity labeling-bioorthogonal conjugation as a chemical approach in medicinal chemistry and chemical biology. In particular, recent examples of using this strategy for affinity-based protein profiling (AfBPP), drug target identification, binding ensemble profiling, studying endogenous biological molecules, and imaging applications will be presented. Additionally, recent advances in the development of 'all-in-one' compact moieties possessing a photoreactive group and clickable handle will be discussed.

Chemical biology studies on norrisolide

The cellular activity of norrisolide (7), a novel Golgi-vesiculating agent, was dissected as function of its chemical structure. This natural product induces irreversible vesiculation of the Golgi membranes and blocks protein transport at the level of the Golgi. The Golgi localization and fragmentation effects of 7 depend on the presence of the perhydroindane core, while the irreversibility of fragmentation depends on the acetyl group of 7. We show that fluorescent derivatives of norrisolide are able to localize to the Golgi apparatus and represent important tools for the study of the Golgi structure and function.

Binding ensemble profiling with photoaffinity labeling (BEProFL) approach: mapping the binding poses of HDAC8 inhibitors

A binding ensemble profiling with (f)photoaffinity labeling (BEProFL) approach that utilizes photolabeling of HDAC8 with a probe containing a UV-activated aromatic azide, mapping of the covalent modifications by liquid chromatography-tandem mass spectrometry, and a computational method to characterize the multiple binding poses of the probe is described. By use of the BEProFL approach, two distinct binding poses of the HDAC8 probe were identified. The data also suggest that an "upside-down" pose with the surface binding group of the probe bound in an alternative pocket near the catalytic site may contribute to the binding.

Trifunctional norrisolide probes for the study of Golgi vesiculation

Inspired by the effect of norrisolide on the Golgi complex, we synthesized norrisolide probes that contain: the perhydroindane core of the parent natural product for Golgi localization, a crosslinking unit (aryl azide or epoxide) for covalent binding to the target, and a tag (biotin or iodine) for subsequent target purification. We found that biotin-containing probes 14, 20 and 24 induced inefficient Golgi vesiculation. However, the iodinated probe 25 induced extensive and irreversible Golgi fragmentation. This probe can be used for the isolation of the cellular target of norrisolide.