The ubiquitin system is important for drug discovery, and the discovery of selective small-molecule inhibitors of deubiquitinating enzymes (DUBs) remains an active yet extremely challenging task. With a few exceptions, previously developed inhibitors have been found to bind the evolutionarily conserved catalytic centers of DUBs, resulting in poor selectivity. The small molecule IU1 was the first-ever specific inhibitor identified and exhibited surprisingly excellent selectivity for USP14 over other DUBs. However, the molecular mechanism for this selectivity was elusive. Herein, we report the high-resolution co-crystal structures of the catalytic domain of USP14 bound to IU1 and three IU1 derivatives. All the structures of these complexes indicate that IU1 and its analogs bind to a previously unknown steric binding site in USP14, thus blocking the access of the C-terminus of ubiquitin to the active site of USP14 and abrogating USP14 activity. Importantly, this steric site in USP14 is very unique, as suggested by structural alignments of USP14 with several known DUB X-ray structures. These results, in conjunction with biochemical characterization, indicate a coherent steric blockade mechanism for USP14 inhibition by compounds of the IU series. In light of the recent report of steric blockade of USP7 by FT671, this work suggests a potential generally applicable allosteric mechanism for the regulation of DUBs via steric blockade, as showcased by our discovery of IU1-248 which is 10-fold more potent than IU1.

A novel three-layered catalyst was successfully synthesized by the copolymerization of divinylbenzene and vinyl benzyl chloride in the presence of 3-mercaptopropyltrimethoxysilane-functionalized magnetic nanoparticles (MNPs) followed by quaternization reaction with N-propyl imidazole and alkaline ion exchange, aiming at improving the recyclability of MNPs supported catalysts. The results obtained by FTIR, TG/DTA, SEM, TEM, DLS, and VSM showed that the prepared catalyst consisted of a catalytic layer, protective layer, and magnetic core. The investigation of catalytic performance indicated that the catalyst displayed a remarkable activity for Knoevenagel condensation due to the large amount of OH − ions loading on the surface and a lower activation energy than that of NaOH, but it was sensitive to the polarity of solvent. Furthermore, the existence of a protective layer incorporated between the MNPs and the catalytic layer provided a good way to avoid the corrosion of magnetic nanoparticles, and the catalyst exhibited good stability in alkaline medium. The catalyst could be recycled by an external magnet at least six times without significant change.

New synthetic strategies that exploited the strengths of both chemoselective ligation and recombinant protein expression were developed to prepare K27 di-ubiquitins (diUb), which enabled mechanistic studies on the molecular recognition of K27-linked Ubs by single-molecule Fçrster resonance energy transfer (smFRET) and X-ray crystallography.The results revealed that free K27 diUb adopted acompact conformation, whereas upon binding to UCHL3, K27 diUb was remodeled to an open conformation. The K27 isopeptide bond remained rigidly buried inside the diUb moiety during binding,a ni nteresting unique structural feature that may explain the distinctive biological function of K27 Ub chains.

Pt-based electrocatalysts are essential to direct methanol fuel cells (DMFCs), but their sluggish reaction kinetics, poor stability, inefficient Pt utilization and susceptibility to CO poisoning hamper the widespread application of...

New synthetic strategies that exploited the strengths of both chemoselective ligation and recombinant protein expression were developed to prepare K27 di-ubiquitins (diUb), which enabled mechanistic studies on the molecular recognition of K27-linked Ubs by single-molecule Fçrster resonance energy transfer (smFRET) and X-ray crystallography.The results revealed that free K27 diUb adopted acompact conformation, whereas upon binding to UCHL3, K27 diUb was remodeled to an open conformation. The K27 isopeptide bond remained rigidly buried inside the diUb moiety during binding,a ni nteresting unique structural feature that may explain the distinctive biological function of K27 Ub chains.