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Remarkably Stereospecific Utilization of ATP ?,?-Halomethylene Analogues by Protein Kinases.

ABSTRACT: ATP analogues containing a CXY group in place of the ?,?-bridging oxygen atom are powerful chemical probes for studying ATP-dependent enzymes. A limitation of such probes has been that conventional synthetic methods generate a mixture of diastereomers when the bridging carbon substitution is nonequivalent (X ? Y). We report here a novel method based on derivatization of a bisphosphonate precursor with a d-phenylglycine chiral auxiliary that enables preparation of the individual diastereomers of ?,?-CHF-ATP and ?,?-CHCl-ATP, which differ only in the configuration at the CHX carbon. When tested on a dozen divergent protein kinases, these individual diastereomers exhibit remarkable diastereospecificity (up to over 1000-fold) in utilization by the enzymes. This high selectivity can be exploited in an enzymatic approach to obtain the otherwise inaccessible diastereomers of ?,?-CHBr-ATP. The crystal structure of a tyrosine kinase Src bound to ?,?-CHX-ADP establishes the absolute configuration of the CHX carbon and helps clarify the origin of the remarkable diastereospecificity observed. We further synthesized the individual diastereomers of ?,?-CHF-?-thiol-ATP and demonstrated their utility in labeling a wide spectrum of kinase substrates. The novel ATP substrate analogues afforded by these two complementary strategies should have broad application in the study of the structure and function of ATP-dependent enzymes.

SUBMITTER: Ni F

PROVIDER: S-EPMC5541949 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature

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Remarkably Stereospecific Utilization of ATP α,β-Halomethylene Analogues by Protein Kinases.

Ni Feng F Kung Alvin A Duan Yankun Y Shah Vivek V Amador Carolina D CD Guo Ming M Fan Xuegong X Chen Lin L Chen Yongheng Y McKenna Charles E CE Zhang Chao C

Journal of the American Chemical Society 20170602 23

ATP analogues containing a CXY group in place of the α,β-bridging oxygen atom are powerful chemical probes for studying ATP-dependent enzymes. A limitation of such probes has been that conventional synthetic methods generate a mixture of diastereomers when the bridging carbon substitution is nonequivalent (X ≠ Y). We report here a novel method based on derivatization of a bisphosphonate precursor with a d-phenylglycine chiral auxiliary that enables preparation of the individual diastereomers of ...[more]

PMID: 28535041

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Project description:BACKGROUND:(-)-Balanol is an ATP mimic that inhibits protein kinase C (PKC) isozymes and cAMP-dependent protein kinase (PKA) with limited selectivity. While PKA is a tumour promoter, PKC isozymes act as tumour promoters or suppressors, depending on the cancer type. In particular, PKC? is frequently implicated in cancer promotion, making it a potential target for anticancer drugs. To improve isozyme selectivity of balanol, exhaustive structural and activity relationship (SAR) studies have been performed in the last two decades, but with limited success. More recently, fluorination on balanol has shown improved selectivity for PKC?, although the fluorine effect is not yet clearly understood. Understanding the origin to this fluorine-based selectivity will be valuable for designing better balanol-based ATP mimicking inhibitors. Computational approaches such as molecular dynamics (MD) simulations can decipher the fluorine effect, provided that correct charges have been assigned to a ligand. Balanol analogues have multiple ionisable functional groups and the effect of fluorine substitutions on the exact charge state of each analogue bound to PKA and to PKC? needs to be thoroughly investigated in order to design highly selective inhibitors for therapeutic applications. RESULTS:We explored the charge states of novel fluorinated balanol analogues using MD simulations. For different potential charge states of these analogues, Molecular Mechanics Generalized Born Surface Area (MMGBSA) binding energy values were computed. This study suggests that balanol and the most potent fluorinated analogue (5S fluorine substitution on the azepane ring), have charges on the azepane ring (N1), and the phenolic (C6''OH) and the carboxylate (C15''O2H) groups on the benzophenone moiety, when bound to PKC? as well as PKA. CONCLUSIONS:To the best our knowledge, this is the first study showing that the phenolate group is charged in balanol and its analogues binding to the ATP site of PKC?. Correct charge assignments of ligands are important to obtain predicted binding energy values from MD simulations that reflect experimental values. Both fluorination and the local enzymatic environment of the ATP site can influence the exact charge states of balanol analogues. Overall, this study is highly valuable for further rational design of potent balanol analogues selective to PKC?.

Project description:Many protein activities are driven by ATP binding and hydrolysis. Here, we explore the ATP binding proteome of the model plant Arabidopsis thaliana using Acyl-ATP (AcATP) probes. These probes target ATP binding sites and covalently label lysine residues in the ATP binding pocket. Protein extracts were labelled with NHS-LC-Biotin, purified over neutravidin and eluted with formic acid. Eluted proteins were separated by 1-D SDS Gel and digested with Trypsin. Peptide mixtures were analysed by LC-MS/MS on an LTQ Velos. Spectra were searched using Mascot 2.3 using a fixed modification of cysteine (57.02 Da for carbamidomethyl), and variable modifications of methionine (15.99 Da for oxidation) and lysine (339.16 and 355.16 Da for BHAc and OBHAc labeling, respectively). A mass tolerance was set to 0.3 Da for the precursor ions and 0.4 Da for fragment ions. Up to two mis-cleavages for trypsin were permitted since the labeling would prevent cleavage at the labeled lysine. The MS2 spectra were searched against the TAIR10_pep_2012 (version November 2012) containing 35386 proteins of Arabidopsis thaliana, supplemented with a small database with 1095 artefact proteins and a reversed decoy database of the same proteins (totals 72962 entries). An oxidized version of the modifier was observed. Alternatively Arabidopsis leaf proteome was labeled with desthiobiotin-acyl ATP and digested with trypsin. Labeled peptides were purified on streptavidin matrix and sequenced by LC-MS/MS on an LTQ linear ion trap. Here the MS2 spectra were searched using SEQUEST against the TAIR9_pep_20090619 database (version June 2009) containing 32,769 proteins of Arabidopsis thaliana. MS2 searches included fixed iodoacetamide modification of cysteine (57 Da for alkylation), and variable modifications of methionine (16 Da for oxidation) and lysine (196 Da for DBAcATP labeling). Up to three mis-cleavages with trypsin were allowed and non-tryptic or half-tryptic peptides were excluded. A mass tolerance was set to 3 Da for the precursor ions and 1 Da for fragment ions.

Dataset Information

Remarkably Stereospecific Utilization of ATP ?,?-Halomethylene Analogues by Protein Kinases.

Publications

Remarkably Stereospecific Utilization of ATP α,β-Halomethylene Analogues by Protein Kinases.

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