Fragment and Conquer: From Structure to Complexes to Function

In this issue of Structure, Shumilin and colleagues show the power of metabolite screening by means of X-ray crystallography to link an orphan protein domain with an orphan biochemical function. This result paves the way for large-scale functional annotation and sets new objectives for structural genomics

e-Drug3D: 3D structure collections dedicated to drug repurposing and fragment-based drug design

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The Ellagitannin Metabolite Urolithin C is a Glucose‐Dependent Regulator of Insulin Secretion through activation of L‐type Calcium Channels

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A Tiny Change Makes a Big Difference in the Anti-Parasitic Activities of an HDAC Inhibitor

International audienceWe previously synthesized an hydroxamate derivative (N-hydroxy-4-[2-(3- methoxyphenyl)acetamido]benzamide) named 363 with potent anti-Toxoplasma gondii activity and histone deacetylase inhibitor (HDACi) effects. Here we show that 1-N-hydroxy-4-N- [(2-methoxyphenyl)methyl]benzene-1,4-dicarboxamide, a 363 isomer, does not have antiparasitic potency and has a 13-fold decrease in HDACi activity. The in silico modeling of T. gondii HDACs of the type II strain discloses identity varying from 25% to 62% on more than 250 residues for S8EP32_TOXG and A0A125YPH4_TOXGM. We observed a high conservation degree with the human HDAC2 (53% and 64% identity, respectively) and a moderate one with the human HDAC8 (30-40%). Two other TgHDACs, S8F6L4_TOXGM and S8GEI3_TOXGM, were identified as displaying a higher similarity with some bacterial orthologs (~35%) than with the human enzymes (~25%). The docking in parallel of the two compounds on the models generated allowed us to gain insights on the docking of these hydroxamate derivatives that guide their specificity and potency against T. gondii histone deacetylase. This information would constitute the rationale from which more specific derivatives can be synthetized

Comparing Binding Modes of Analogous Fragments Using NMR in Fragment-Based Drug Design: Application to PRDX5

International audienceFragment-based drug design is one of the most promising approaches for discovering novel and potent inhibitors against therapeutic targets. The first step of the process consists of identifying fragments that bind the protein target. The determination of the fragment binding mode plays a major role in the selection of the fragment hits that will be processed into drug-like compounds. Comparing the binding modes of analogous fragments is a critical task, not only to identify specific interactions between the protein target and the fragment, but also to verify whether the binding mode is conserved or differs according to the fragment modification. While X-ray crystallography is the technique of choice, NMR methods are helpful when this fails. We show here how the ligand-observed saturation transfer difference (STD) experiment and the protein-observed 15N-HSQC experiment, two popular NMR screening experiments, can be used to compare the binding modes of analogous fragments. We discuss the application and limitations of these approaches based on STD-epitope mapping, chemical shift perturbation (CSP) calculation and comparative CSP sign analysis, using the human peroxiredoxin 5 as a protein model

Protein–ligand structure guided by backbone and side-chain proton chemical shift perturbations

International audienceThe fragment-based drug design approach consists of screening libraries of fragment-like ligands, to identify hits that typically bind the protein target with weak affinity ( 100μM –5 mM). The determination of the protein–fragment complex 3D structure constitutes a crucial step for uncovering the key interactions responsible for the protein–ligand recognition, and for growing the initial fragment into potent active compounds. The vast majority of fragments are aromatic compounds that induce chemical shift perturbations (CSP) on protein NMR spectra. These experimental CSPs can be quantitatively used to guide the ligand docking, through the comparison between experimental CSPs and CSP back-calculation based on the ring current effect. Here we implemented the CSP back-calculation into the scoring function of the program PLANTS. We compare the results obtained with CSPs measured either on amide or aliphatic protons of the human peroxiredoxin 5. We show that the different kinds of protons lead to different results for resolving the 3D structures of protein–fragment complexes, with the best results obtained with the Hα protons

Vpr expression abolishes the capacity of HIV-1 infected cells to repair uracilated DNA

International audienceThe human immunodeficiency virus type 1 (HIV-1) Vpr protein binds to the cellular uracil-DNA glycosylase UNG2 and induces its degradation through the assembly with the DDB1-CUL4 ubiquitin ligase complex. This interaction counteracts the antiviral activity exerted by UNG2 on HIV-1 gene transcription, as previously reported by us. In this work, we show that Vpr expression in the context of HIV-1 infection markedly decreases UNG2 expression in transformed or primary CD4 + T lymphocytes. We demonstrate for the first time that Vpr-UNG2 interaction significantly impairs the uracil excision activity of infected cells. The loss of uracil excision activity coincides with a significant accumulation of uracilated bases in the genome of infected cells without changes in cell division. Although UNG2 expression and uracil-DNA glycosylase activity are recovered after the peak of retroviral replication, the mutagenic effect of transient DNA uracilation in cycling cells should be taken into account. Therefore, the possible consequences of Vpr-mediated temporary depletion of endo-genous nuclear UNG2 and subsequent alteration of the genomic integrity of infected cells need to be evaluated in the physiopathogenesis of HIV infection