scholarly journals Ferritin Conjugates With Multiple Clickable Amino Acids Encoded by C-Terminal Engineered Pyrrolysyl-tRNA Synthetase

2021 ◽  
Vol 9 ◽  
Author(s):  
Yi-Hui Wang ◽  
Mu-Lung Jian ◽  
Pei-Jung Chen ◽  
Jo-Chu Tsou ◽  
Le P. Truong ◽  
...  
Keyword(s):  
Click Reaction ◽  
Trna Synthetase ◽  
Delivery Systems ◽  
Her2 Receptor ◽  
Site Specific ◽  
Protein Cage ◽  
Specific Loading ◽  
Wide Range ◽  
Multiple Drugs ◽  
A Site

This study reports the application of expanding genetic codes in developing protein cage-based delivery systems. The evolved Methanosarcina mazei pyrrolysyl-tRNA synthetase (PylRS)•tRNAPyl pairs derived from directed evolution are examined to probe their recognition for para-substituted phenylalanine analogs. The evolved MmPylRS, AzFRS, harboring a wide range of substrates, is further engineered at the C-terminal region into another variant, AzFRS-MS. AzFRS-MS shows suppression of the elevated sfGFP protein amount up to 10 TAG stop codons when charging p-azido-l-phenylalanine (AzF, 4), which allows the occurrence of click chemistry. Since protein nanocages used as drug delivery systems that encompass multiple drugs through a site-specific loading approach remain largely unexplored, as a proof of concept, the application of AzFRS-MS for the site-specific incorporation of AzF on human heavy chain ferritin (Ftn) is developed. The Ftn-4 conjugate is shown to be able to load multiple fluorescence dyes or a therapeutic agent, doxorubicin (Dox), through the strain-promoted azide-alkyne cycloaddition (SPAAC) click reaction. Aiming to selectively target Her2+ breast cancer cells, Ftn-4-DOX conjugates fused with a HER2 receptor recognition peptide, anti-Her2/neu peptide (AHNP), is developed and demonstrated to be able to deliver Dox into the cell and to prolong the drug release. This work presents another application of evolved MmPylRS systems, whose potential in developing a variety of protein conjugates is noteworthy.

Optimization of the posttranslational click modification of proteins

2011 ◽  
Vol 76 (9) ◽  
pp. 1089-1101
Author(s):  
Milan Vrabel ◽  
Emine Kaya ◽  
Stefan Prill ◽  
Veronika Ehmke ◽  
Thomas Carell
Keyword(s):  
Mass Spectrometry ◽  
Amino Acids ◽  
Fluorescent Protein ◽  
Click Reaction ◽  
Yellow Fluorescent Protein ◽  
Trna Synthetase ◽  
Site Specific ◽  
Specific Manner ◽  
Modified Proteins ◽  
A Site

In order to develop efficient methods that would enable the synthesis of posttranslationaly modified proteins in a site-specific manner we have adopted the orthogonal pyrrolysyl-tRNA synthetase/tRNA pair to genetically encode various pyrrolysine analogs, which we were able to insert into the yellow fluorescent protein (YFP). These experiments showed that the alkene and alkyne containing amino acids 5 and 6 are superior substrates for the pyrrolysyl-tRNA synthetase and that they can be successfully incorporated into proteins. Using the Cu(I)-catalyzed Huisgen–Meldal–Sharpless click reaction, the alkyne containing YFP was finally glycosylated with various sugars. We confirmed the presence of the modified amino acids as well as the corresponding sugar modifications by HPLC-MS/MS mass spectrometry.

Effect of overburden pressure on liquefaction resistance of sand

1994 ◽  
Vol 31 (1) ◽  
pp. 53-60 ◽  
Author(s):  
V.S. Pillai ◽  
P.M. Byrne
Keyword(s):  
Published Data ◽  
Confining Stress ◽  
Liquefaction Resistance ◽  
Overburden Pressure ◽  
Site Specific ◽  
Indirect Approach ◽  
Cyclic Resistance ◽  
Wide Range ◽  
Cyclic Resistance Ratio ◽  
A Site

The effect of overburden pressure on liquefaction resistance of sand is studied and results of a site-specific investigation are presented. When estimating liquefaction resistance of sand from the indirect approach using the chart suggested by Seed et al. (1984) a correction factor Kσ is applied to account for vertical effective overburden stresses larger than 1 tsf. Published data indicate a decrease in Kσ with increased confining stress but with a wide range of Kσ values for the same confining stresses, predicting significantly differing liquefaction resistance. The effect of confining stresses on liquefaction resistance was investigated as part of a comprehensive seismic assessment of Duncan Dam in British Columbia. The results indicate that Kσ is dependent on confining stresses and the relative density of the soil, and values are generally significantly higher than much of the previously published data. Key words : liquefaction, sand, confining stress, density, cyclic resistance ratio.

scholarly journals Site Specific Genetic Incorporation of Azidophenylalanine in Schizosaccharomyces pombe

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Nan Shao ◽  
N. Sadananda Singh ◽  
Susan E. Slade ◽  
Alexandra M. E. Jones ◽  
Mohan K. Balasubramanian
Keyword(s):  
Amino Acids ◽  
Schizosaccharomyces Pombe ◽  
Unnatural Amino Acids ◽  
Building Blocks ◽  
Trna Synthetase ◽  
Cross Linking ◽  
Site Specific ◽  
Specific Manner ◽  
Protein Functions ◽  
A Site

Abstract The diversity of protein functions is impacted in significant part by the chemical properties of the twenty amino acids, which are used as building blocks for nearly all proteins. The ability to incorporate unnatural amino acids (UAA) into proteins in a site specific manner can vastly expand the repertoire of protein functions and also allows detailed analysis of protein function. In recent years UAAs have been incorporated in a site-specific manner into proteins in a number of organisms. In nearly all cases, the amber codon is used as a sense codon and an orthogonal tRNA/aminoacyl-tRNA synthetase (RS) pair is used to generate amber suppressing tRNAs charged with the UAA. In this work, we have developed tools to incorporate the cross-linking amino acid azido-phenylalanine (AzF) through the use of bacterial tRNATyr and a modified version of TyrRS, AzFRS, in Schizosaccharomyces pombe, which is an attractive model organism for the study of cell behavior and function. We have incorporated AzF into three different proteins. We show that the majority of AzF is modified to amino-phenyl alanine, but protein cross-linking was still observed. These studies set the stage for exploitation of this new technology for the analysis of S. pombe proteins.

scholarly journals Site-specific analysis of N-glycans from different sheep prion strains

2021 ◽  
Vol 17 (2) ◽  
pp. e1009232
Author(s):  
Natali Nakić ◽  
Thanh Hoa Tran ◽  
Mislav Novokmet ◽  
Olivier Andreoletti ◽  
Gordan Lauc ◽  
...  
Keyword(s):  
Prion Protein ◽  
Prion Diseases ◽  
Mammalian Species ◽  
Site Specific ◽  
Prion Strains ◽  
Glycosylation Sites ◽  
Specific Analysis ◽  
Wide Range ◽  
The One ◽  
A Site

Prion diseases are a group of neurodegenerative diseases affecting a wide range of mammalian species, including humans. During the course of the disease, the abnormally folded scrapie prion protein (PrPSc) accumulates in the central nervous system where it causes neurodegeneration. In prion disorders, the diverse spectrum of illnesses exists because of the presence of different isoforms of PrPSc where they occupy distinct conformational states called strains. Strains are biochemically distinguished by a characteristic three-band immunoblot pattern, defined by differences in the occupancy of two glycosylation sites on the prion protein (PrP). Characterization of the exact N-glycan structures attached on either PrPC or PrPSc is lacking. Here we report the characterization and comparison of N-glycans from two different sheep prion strains. PrPSc from both strains was isolated from brain tissue and enzymatically digested with trypsin. By using liquid chromatography coupled to electrospray mass spectrometry, a site-specific analysis was performed. A total of 100 structures were detected on both glycosylation sites. The N-glycan profile was shown to be similar to the one on mouse PrP, however, with additional 40 structures reported. The results presented here show no major differences in glycan composition, suggesting that glycans may not be responsible for the differences in the two analyzed prion strains.

scholarly journals Polyspecific monoclonal lupus autoantibodies reactive with both polynucleotides and phospholipids.

1981 ◽  
Vol 153 (4) ◽  
pp. 897-909 ◽  
Author(s):  
E M Lafer ◽  
J Rauch ◽  
C Andrzejewski ◽  
D Mudd ◽  
B Furie ◽  
...  
Keyword(s):  
Test System ◽  
Activated Partial Thromboplastin Time ◽  
Biological Molecules ◽  
Spleen Cells ◽  
Phosphatidyl Glycerol ◽  
Site Specific ◽  
Wide Range ◽  
A Site ◽  
Idiotypic Antibody ◽  
Phosphate Groups

Hybridomas the produce anti-DNA autoantibodies were prepared from spleen cells of unimmunized MRL/1 mice, a strain that spontaneously develops severe systemic lupus erythematous (SLE). Reactivities of these monoclonal antibodies with a wide range of polynucleotides prompted tests of their reactions with phospholipids which, like polynucleotides, contain diester-linked phosphate groups in their backbones. In competitive radioimmunoassays, cardiolipin, phosphatidic acid, and phosphatidyl glycerol blocked the binding of these hybridoma antibodies to denatured DNA. These phospholipids also specifically inhibited the reaction between a hybridoma antibody and a site-specific anti-idiotypic antibody. The antinuclear reaction of one of these antibodies was specifically inhibited by cardiolipin. This same antibody prolonged the activated partial thromboplastin time in a manner characteristic of a lupus anticoagulant, presumably by binding to phospholipid in the test system. The polyspecific reactivity of a single molecular species of lupus autoantibody suggests that some of the diverse serological abnormalities of SLE may be a result of the binding of certain autoantibodies to a phosphodiester-containing epitope that is present in diverse biological molecules.

Systematic Engineering of a Protein Nanocage for High-Yield, Site-Specific Modification

2018 ◽  
Author(s):  
Daniel D. Brauer ◽  
Emily C. Hartman ◽  
Daniel L.V. Bader ◽  
Zoe N. Merz ◽  
Danielle Tullman-Ercek ◽  
...  
Keyword(s):  
Small Molecules ◽  
Protein Modification ◽  
Positive Charge ◽  
Specific Protein ◽  
High Yield ◽  
Site Specific ◽  
Protein Cage ◽  
Protein Carriers ◽  
Site Selective ◽  
Targeted Library

<div> <p>Site-specific protein modification is a widely-used strategy to attach drugs, imaging agents, or other useful small molecules to protein carriers. N-terminal modification is particularly useful as a high-yielding, site-selective modification strategy that can be compatible with a wide array of proteins. However, this modification strategy is incompatible with proteins with buried or sterically-hindered N termini, such as virus-like particles like the well-studied MS2 bacteriophage coat protein. To assess VLPs with improved compatibility with these techniques, we generated a targeted library based on the MS2-derived protein cage with N-terminal proline residues followed by three variable positions. We subjected the library to assembly, heat, and chemical selections, and we identified variants that were modified in high yield with no reduction in thermostability. Positive charge adjacent to the native N terminus is surprisingly beneficial for successful extension, and over 50% of the highest performing variants contained positive charge at this position. Taken together, these studies described nonintuitive design rules governing N-terminal extensions and identified successful extensions with high modification potential.</p> </div>

Spectroscopic Studies of Asparaginyl-tRNA Synthetase from Entamoeba histolytica

2019 ◽  
Vol 26 (6) ◽  
pp. 435-448
Author(s):  
Priyanka Biswas ◽  
Dillip K. Sahu ◽  
Kalyanasis Sahu ◽  
Rajat Banerjee
Keyword(s):  
Circular Dichroism ◽  
Steady State ◽  
Entamoeba Histolytica ◽  
Protein Concentration ◽  
Trna Synthetase ◽  
Solvent Exposure ◽  
Steady State Fluorescence ◽  
State Process ◽  
Wide Range ◽  
Circular Dichroïsm

Background: Aminoacyl-tRNA synthetases play an important role in catalyzing the first step in protein synthesis by attaching the appropriate amino acid to its cognate tRNA which then transported to the growing polypeptide chain. Asparaginyl-tRNA Synthetase (AsnRS) from Brugia malayi, Leishmania major, Thermus thermophilus, Trypanosoma brucei have been shown to play an important role in survival and pathogenesis. Entamoeba histolytica (Ehis) is an anaerobic eukaryotic pathogen that infects the large intestines of humans. It is a major cause of dysentery and has the potential to cause life-threatening abscesses in the liver and other organs making it the second leading cause of parasitic death after malaria. Ehis-AsnRS has not been studied in detail, except the crystal structure determined at 3 Å resolution showing that it is primarily α-helical and dimeric. It is a homodimer, with each 52 kDa monomer consisting of 451 amino acids. It has a relatively short N-terminal as compared to its human and yeast counterparts. Objective: Our study focusses to understand certain structural characteristics of Ehis-AsnRS using biophysical tools to decipher the thermodynamics of unfolding and its binding properties. Methods: Ehis-AsnRS was cloned and expressed in E. coli BL21DE3 cells. Protein purification was performed using Ni-NTA affinity chromatography, following which the protein was used for biophysical studies. Various techniques such as steady-state fluorescence, quenching, circular dichroism, differential scanning fluorimetry, isothermal calorimetry and fluorescence lifetime studies were employed for the conformational characterization of Ehis-AsnRS. Protein concentration for far-UV and near-UV circular dichroism experiments was 8 µM and 20 µM respectively, while 4 µM protein was used for the rest of the experiments. Results: The present study revealed that Ehis-AsnRS undergoes unfolding when subjected to increasing concentration of GdnHCl and the process is reversible. With increasing temperature, it retains its structural compactness up to 45ºC before it unfolds. Steady-state fluorescence, circular dichroism and hydrophobic dye binding experiments cumulatively suggest that Ehis-AsnRS undergoes a two-state transition during unfolding. Shifting of the transition mid-point with increasing protein concentration further illustrate that dissociation and unfolding processes are coupled indicating the absence of any detectable folded monomer. Conclusion: This article indicates that GdnHCl induced denaturation of Ehis-AsnRS is a two – state process and does not involve any intermediate; unfolding occurs directly from native dimer to unfolded monomer. The solvent exposure of the tryptophan residues is biphasic, indicating selective quenching. Ehis-AsnRS also exhibits a structural as well as functional stability over a wide range of pH.

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