Overcoming peri- and ortho-Selectivity in C−H Methylation of 1-Naphthaldehydes by Tunable Transient Ligand Strategy

Prenylation plays an important role in diversifying structure and function of secondary metabolites. Although several cyanobactin prenyltransferases have been characterized, their modes of action are mainly limited to the modification of electron-rich hetero atoms. Here we report a unique prenyltransferase originating from Limnothrix sp. CACIAM 69d, referred to as LimF, which catalyzes an unprecedented His-C-geranylation. Interestingly, LimF executes the geranylation on not only its native peptide substrate but also a wide range of exotic peptides, including thioether-closed macrocycles. We have also serendipitously uncovered an ability of Tyr-O-geranylation as the secondary function of LimF, indicating it is an unusual bifunctional prenyltransferase. Crystallographic analysis of LimF complexed with a pentapeptide substrate and a prenyl donor analog provides structural basis for its unique His recognition and its bifunctionality. Lastly, we show the LimF’s prenylation ability on various bioactive molecules containing an imidazole group, highlighting its potential as a versatile biocatalyst for site-specific geranylation.

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Site-specific methylation in Bacillus subtilis chemotaxis: effect of covalent modifications to the chemotaxis receptor McpB

Microbiology ◽

10.1099/mic.0.044685-0 ◽

2011 ◽

Vol 157 (1) ◽

pp. 56-65 ◽

Cited By ~ 11

Author(s):

George D. Glekas ◽

Joseph R. Cates ◽

Theodore M. Cohen ◽

Christopher V. Rao ◽

George W. Ordal

Keyword(s):

Bacillus Subtilis ◽

Electrostatic Interactions ◽

Methyl Groups ◽

Receptor Function ◽

Site Specific ◽

Apparent Affinity ◽

Covalent Modifications ◽

The One ◽

A Site ◽

Homology Models

The Bacillus subtilis chemotaxis pathway employs a receptor methylation system that functions differently from the one in the canonical Escherichia coli pathway. Previously, we hypothesized that B. subtilis employs a site-specific methylation system for adaptation where methyl groups are added and removed at different sites. This study investigated how covalent modifications to the adaptation region of the chemotaxis receptor McpB altered its apparent affinity for its cognate ligand, asparagine, and also its ability to activate the CheA kinase. This receptor has three closely spaced adaptation sites located at residues Gln371, Glu630 and Glu637. We found that amidation, a putative methylation mimic, of site 371 increased the receptor's apparent affinity for asparagine and its ability to activate the CheA kinase. Conversely, amidation of sites 630 and 637 reduced the receptor's ability to activate the kinase but did not affect the apparent affinity for asparagine, suggesting that activity and sensitivity are independently controlled in B. subtilis. We also examined how electrostatic interactions may underlie this behaviour, using homology models. These findings further our understanding of the site-specific methylation system in B. subtilis by demonstrating how the modification of specific sites can have varying effects on receptor function.

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An Advanced Review on Resealed Erythrocytes

Asian Journal of Pharmaceutical Research and Development ◽

10.22270/ajprd.v7i6.606 ◽

2019 ◽

Vol 7 (6) ◽

pp. 55-61

Author(s):

Gousia S. Begum ◽

Mustafa D

Keyword(s):

Drug Delivery ◽

Drug Delivery Systems ◽

Drug Loading ◽

Bioactive Molecules ◽

Specific Drug ◽

Site Specific ◽

Enzyme Replacement ◽

Effective Delivery ◽

Novel Drug ◽

Carrier Systems

Now a days there are numerous applications have been proposed for the use of resealed erythrocytes as carrier for drugs, enzyme replacement therapy etc. Until other carrier systems come of age, resealed erythrocytes technology will remain an active field for the further research. The use of resealed erythrocytes shows potential for a safe and effective delivery of various bioactive molecules for effective targeting. In coming future, erythrocyte based drug delivery system with their capability to afford controlled and site specific drug delivery have been developed for disease management. Erythrocyte carriers are “Nano devices in the field of Nanotechnology”. A large amount of valuable work is needed so as to utilize the potentials of erythrocytes in passive as well as active targeting of drugs in diseases like cancer. At present erythrocytes are most effective carriers in novel drug delivery systems considering their tremendous potential. Hence the present article is reviewed about method of drug loading, evaluation and applications of RSE.

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Site-specific dynamics of methyl groups probed by temporal evolution of heteronuclear 13C{1H} Overhauser polarisation encoded in 13C – 13C solid-state NMR correlation experiments

Chemical Physics Letters ◽

10.1016/j.cplett.2020.137628 ◽

2020 ◽

Vol 754 ◽

pp. 137628

Author(s):

Rudra N. Purusottam ◽

Piotr Tekely

Keyword(s):

Solid State ◽

Solid State Nmr ◽

Temporal Evolution ◽

Methyl Groups ◽

Site Specific

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Heteronuclear Cross-Relaxation under Dynamic Nuclear Polarization in Nicotine and Caffeine

Experimental Results ◽

10.1017/exp.2020.17 ◽

2020 ◽

Vol 1 ◽

Author(s):

V. Aladin ◽

P. A. Trenkler ◽

B. Corzilius

Keyword(s):

Dynamic Nuclear Polarization ◽

Nuclear Polarization ◽

Sensitivity Enhancement ◽

Magic Angle Spinning ◽

Cross Relaxation ◽

Methyl Groups ◽

Magic Angle ◽

Site Specific ◽

Reorientation Dynamics ◽

Angle Spinning

AbstractDynamic nuclear polarization (DNP) is a technique in magic-angle spinning (MAS) nuclear magnetic resonance (NMR) which leads to sensitivity enhancement and helps to overcome the issue of low polarization in detected nuclei. Recent research showed, that methyl groups, which show active reorientation dynamics and cause heteronuclear cross relaxation at typical DNP temperatures around 100 K, may be used as a pinpoint source of polarization for selective and site-specific probing. In this study, we investigated the cross-relaxation behavior of methyl groups in nicotine and caffeine under DNP. These effects could be useful for investigating receptor/ligand binding.

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Large-cluster and combined fluorescent and gold immunoprobes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100166920 ◽

1996 ◽

Vol 54 ◽

pp. 892-893

Author(s):

Richard D. Powell ◽

James F. Hainfeld ◽

Carol M. R. Halsey ◽

David L. Spector ◽

Shelley Kaurin ◽

...

Keyword(s):

Metal Cluster ◽

Sulfonyl Chloride ◽

Gel Filtration ◽

Cross Linking ◽

Site Specific ◽

Fab Fragments ◽

Cluster Label ◽

Covalently Linked ◽

Texas Red ◽

Fold Excess

Two new types of covalently linked, site-specific immunoprobes have been prepared using metal cluster labels, and used to stain components of cells. Combined fluorescein and 1.4 nm “Nanogold” labels were prepared by using the fluorescein-conjugated tris (aryl) phosphine ligand and the amino-substituted ligand in the synthesis of the Nanogold cluster. This cluster label was activated by reaction with a 60-fold excess of (sulfo-Succinimidyl-4-N-maleiniido-cyclohexane-l-carboxylate (sulfo-SMCC) at pH 7.5, separated from excess cross-linking reagent by gel filtration, and mixed in ten-fold excess with Goat Fab’ fragments against mouse IgG (obtained by reduction of F(ab’)2 fragments with 50 mM mercaptoethylamine hydrochloride). Labeled Fab’ fragments were isolated by gel filtration HPLC (Superose-12, Pharmacia). A combined Nanogold and Texas Red label was also prepared, using a Nanogold cluster derivatized with both and its protected analog: the cluster was reacted with an eight-fold excess of Texas Red sulfonyl chloride at pH 9.0, separated from excess Texas Red by gel filtration, then deprotected with HC1 in methanol to yield the amino-substituted label.

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The challenge of detecting modifications on proteins

Essays in Biochemistry ◽

10.1042/ebc20190055 ◽

2020 ◽

Vol 64 (1) ◽

pp. 135-153 ◽

Cited By ~ 1

Author(s):

Lauren Elizabeth Smith ◽

Adelina Rogowska-Wrzesinska

Keyword(s):

Mass Spectrometry ◽

Protein Function ◽

Chemical Properties ◽

Lysine Acetylation ◽

Mass Determination ◽

Post Translational Modifications ◽

Site Specific ◽

The Common

Abstract Post-translational modifications (PTMs) are integral to the regulation of protein function, characterising their role in this process is vital to understanding how cells work in both healthy and diseased states. Mass spectrometry (MS) facilitates the mass determination and sequencing of peptides, and thereby also the detection of site-specific PTMs. However, numerous challenges in this field continue to persist. The diverse chemical properties, low abundance, labile nature and instability of many PTMs, in combination with the more practical issues of compatibility with MS and bioinformatics challenges, contribute to the arduous nature of their analysis. In this review, we present an overview of the established MS-based approaches for analysing PTMs and the common complications associated with their investigation, including examples of specific challenges focusing on phosphorylation, lysine acetylation and redox modifications.

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