scholarly journals Allosteric regulation of the proteasomes catalytic sites by the proteasome activator PA28gamma/REGgamma

2021 ◽  
Author(s):  
Taylor A Thomas ◽  
David M Smith
Keyword(s):  
Active Sites ◽  
Quaternary Structure ◽  
Binding Mode ◽  
Catalytic Site ◽  
20S Proteasome ◽  
Substrate Selection ◽  
Peptide Substrates ◽  
Proteasome Activator ◽  
Catalytic Sites ◽  
Alternative Hypotheses

Proteasome Activator 28γ (PA28γ) is a member of the 11S family of proteasomal regulators that is constitutively expressed in the nucleus and is implicated in certain cancers, lupus, rheumatoid arthritis, and Poly-glutamine neurodegenerative diseases. However, how PA28γ functions in protein degradation remains unclear. Though PA28γs mechanism has been investigated for some time, many alternative hypotheses have not been tested: e.g. 1) substrate selection, 2) allosteric upregulation of the Trypsin-like catalytic site, 3) allosteric inhibition of the Chymotrypsin- and Caspase-like catalytic sites, 4) conversion of the Chymotrypsin- or Caspase-like sites to new Trypsin-like catalytic sites, and 5) gate-opening in combination with these. The purpose of this study was to conclusively determine how PA28γ regulates proteasome function. Here, we rigorously and definitively show that PA28γ uses an allosteric mechanism to upregulate the proteolytic activity of the 20S proteasomes Trypsin-like catalytic site. Using a constitutively open channel proteasome, we were able to dissociate gating affects from catalytic affects demonstrating that the PA28γ-increases the affinity (Km) and Vmax for Trypsin-like peptide substrates. Mutagenesis of PA28γ also reveals that it does not select for (i.e. filter) peptide substrates, and does not change the specificity of the other active sites to trypsin-like. Further, using Cryo-EM we were able to visualize the C7 symmetric PA28γ-20S proteasome complex at 4.4A validating it's expected 11S-like quaternary structure and proteasome binding mode. The results of this study provide unambiguous evidence that PA28γ functions by allosterically upregulating the T-L like site in the 20S proteasome.

scholarly journals Insights on forming N,O-coordinated Cu single-atom catalysts for electrochemical reduction CO2 to methane

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yanming Cai ◽  
Jiaju Fu ◽  
Yang Zhou ◽  
Yu-Chung Chang ◽  
Qianhao Min ◽  
...  
Keyword(s):  
Energy Barrier ◽  
Active Sites ◽  
Theoretical Calculations ◽  
High Energy ◽  
Single Atom ◽  
Faradaic Efficiency ◽  
High Energy Barrier ◽  
Catalytic Sites ◽  
Electron Reduction ◽  
First Time

AbstractSingle-atom catalysts (SACs) are promising candidates to catalyze electrochemical CO2 reduction (ECR) due to maximized atomic utilization. However, products are usually limited to CO instead of hydrocarbons or oxygenates due to unfavorable high energy barrier for further electron transfer on synthesized single atom catalytic sites. Here we report a novel partial-carbonization strategy to modify the electronic structures of center atoms on SACs for lowering the overall endothermic energy of key intermediates. A carbon-dots-based SAC margined with unique CuN2O2 sites was synthesized for the first time. The introduction of oxygen ligands brings remarkably high Faradaic efficiency (78%) and selectivity (99% of ECR products) for electrochemical converting CO2 to CH4 with current density of 40 mA·cm-2 in aqueous electrolytes, surpassing most reported SACs which stop at two-electron reduction. Theoretical calculations further revealed that the high selectivity and activity on CuN2O2 active sites are due to the proper elevated CH4 and H2 energy barrier and fine-tuned electronic structure of Cu active sites.

Tuning electronic states of catalytic sites enhances SCR activity of hexagonal WO3by Mo framework substitution

2017 ◽  
Vol 7 (12) ◽  
pp. 2467-2473 ◽  
Author(s):  
Yaxin Chen ◽  
Zichenxi Dong ◽  
Zhiwei Huang ◽  
Meijuan Zhou ◽  
Jiayi Gao ◽  
...  
Keyword(s):  
Active Sites ◽  
Electronic States ◽  
Catalytic Sites ◽  
Catalytically Active

The electronic states of the catalytically active sites of HWO were tuned by Mo framework substitution.

scholarly journals Large-area printing of ferroelectric surface and super-domains for efficient solar water splitting

2020 ◽  
Author(s):  
Yu Tian ◽  
Yaqing Wei ◽  
Minghui Pei ◽  
Rongrong Cao ◽  
Zhenao Gu ◽  
...  
Keyword(s):  
Water Splitting ◽  
Electric Fields ◽  
Electronic Structures ◽  
Active Sites ◽  
Large Area ◽  
Solar Water Splitting ◽  
High Efficient ◽  
Catalytic Sites ◽  
Order Of Magnitude ◽  
Magnitude Increase

Abstract Surface electronic structures of the photoelectrodes determine the activity and efficiency of the photoelectrochemical water splitting, but the controls of their surface structures and interfacial chemical reactions remain challenging. Here, we use ferroelectric BiFeO3 as a model system to demonstrate an efficient and controllable water splitting reaction by large-area constructing the hydroxyls-bonded surface. The up-shift of band edge positions at this surface enables and enhances the interfacial holes and electrons transfer through the hydroxyl-active-sites, leading to simultaneously enhanced oxygen and hydrogen evolutions. Furthermore, printing of ferroelectric super-domains with microscale checkboard up/down electric fields separates the distribution of reduction/oxidation catalytic sites, enhancing the charge separation and giving rise to an order of magnitude increase of the photocurrent. This large-area printable ferroelectric surface and super-domains offer an alternative platform for controllable and high-efficient photocatalysis.

scholarly journals Molecular Docking Study of the Potential Relevance of the Natural Compounds Isoflavone and Myricetin to COVID-19

2021 ◽  
Vol 25 (3) ◽  
pp. 271-282
Author(s):  
Didik Priyandoko ◽  
◽  
Wahyu Widowati ◽  
Mawar Subangkit ◽  
Diana Jasaputra ◽  
...  
Keyword(s):  
Molecular Docking ◽  
Severe Acute Respiratory Syndrome ◽  
Active Sites ◽  
Docking Study ◽  
Binding Mode ◽  
Molecular Docking Study ◽  
Wuhan City ◽  
The World ◽  
Novel Coronavirus ◽  
Proteins Interactions

The 2019 novel coronavirus (2019-nCoV) or severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread rapidly from its origin in Wuhan City, Hubei Province, China, to the rest of the world. The efficacy of herbal treatment in the control of contagious disease was demonstrated during the 2003 outbreak of severe acute respiratory syndrome (SARS). Natural compound used for this study were isoflavone and myricetin. Molecular docking was performed to analyze binding mode of the compounds towards 12 proteins related to COVID-19. The prediction shows that isoflavone and myricetin have moderate probability of antiviral activity. All of the docked compounds occupied the active sites of the proteins related to COVID-19. Based on QSAR and molecular docking, interactions were predicted with 10 out of 12 potential COVID-19 proteins for myricetin and with 9 out of 12 proteins interactions for isoflavone. A potential disease alleviating action is suggested for isoflavone and myricetin in the context of COVID-19 infection.

“Zn-Link”:  A Metal-Sharing Interface that Organizes the Quaternary Structure and Catalytic Site of the Endoribonuclease, RNase E†

Biochemistry ◽  
2005 ◽  
Vol 44 (12) ◽  
pp. 4667-4675 ◽  
Author(s):  
Anastasia J. Callaghan ◽  
Yulia Redko ◽  
Loretta M. Murphy ◽  
J. Günter Grossmann ◽  
David Yates ◽  
...  
Keyword(s):  
Quaternary Structure ◽  
Catalytic Site ◽  
Rnase E

The protease MBTPS2 is an important regulator of several cellular processes, especially in health and sickness

2021 ◽  
Author(s):  
Moataz Dowaidar
Keyword(s):  
Active Sites ◽  
Peptide Bond ◽  
Cellular Processes ◽  
Disease States ◽  
Tremendous Progress ◽  
Catalytic Sites ◽  
Important Regulator ◽  
Catalytic Active Sites ◽  
Proteolytic Action ◽  
Health And Sickness

Since the identification of MBTPS2 in 1997, tremendous progress has been made in determining the protease's functions. The protease has developed from an element of the SREBP cleavage machinery to an important regulator of several cellular processes, especially in health and sickness. With this newfound information from biochemical and structural biology, S2P's proteolytic action through peptide bond hydrolysis can occur in the membrane, providing a conceptual framework for appreciating S2P's roles in other aspects, and showing that many other substrates rely on S2P for their survival. In addition, we discovered the identity of both of S2P's catalytic active sites, an essential finding as the activity of the proteolysis as well as the pathogenesis of MBTPS2-caused illnesses seems to be connected to the molecular and biochemical features of the catalytic sites. Additionally, MBTPS2 causes different diseases, possibly illustrating the pleiotropic nature of the protein. Also, while the ailments reported thus far are all due to mutations that cause MBTPS2 to lose function, other variants that cause MBTPS2 to be hyperactive have not been examined. Nevertheless, recognizing the related sickness pathomechanism is a challenge. Pursuing these challenging technical areas would most definitely enhance our understanding of MBTPS2 in disease states. MBTPS2 appears to be nearing the solution to many of the remaining fundamental questions surrounding the mechanism of its action, as well as being a therapeutic target for new therapies.

scholarly journals Quinazolinones as Competitive Inhibitors of Carbonic Anhydrase-II (Human and Bovine): Synthesis, in-vitro, in-silico, Selectivity, and Kinetics Studies

2020 ◽  
Vol 8 ◽  
Author(s):  
Ajmal Khan ◽  
Majid Khan ◽  
Sobia Ahsan Halim ◽  
Zulfiqar Ali Khan ◽  
Zahid Shafiq ◽  
...  
Keyword(s):  
Carbonic Anhydrase ◽  
Active Sites ◽  
Binding Mode ◽  
Competitive Inhibitor ◽  
Significant Inhibition ◽  
Carbonic Anhydrase Ii ◽  
Complete Agreement ◽  
Active Inhibitor ◽  
Kinetics Studies

Carbonic anhydrase-II (CA-II) is associated with glaucoma, malignant brain tumors, and renal, gastric, and pancreatic carcinomas and is mainly involved in the regulation of the bicarbonate concentration in the eyes. CA-II inhibitors can be used to reduce the intraocular pressure usually associated with glaucoma. In search of potent CA-II inhibitors, a series of quinazolinones derivatives (4a-p) were synthesized and characterized by IR and NMR spectroscopy. The inhibitory potential of all the compounds was evaluated against bovine carbonic anhydrase-II (bCA-II) and human carbonic anhydrase-II (hCA-II), and compounds displayed moderate to significant inhibition with IC50 values of 8.9–67.3 and 14.0–59.6 μM, respectively. A preliminary structure-activity relationship suggested that the presence of a nitro group on the phenyl ring at R position contributes significantly to the overall activity. Kinetics studies of the most active inhibitor, 4d, against both bCA-II and hCA-II were performed to investigate the mode of inhibition and to determine the inhibition constants (Ki). According to the kinetics results, 4d is a competitive inhibitor of bCA-II and hCA-II with Ki values of 13.0 ± 0.013 and 14.25 ± 0.017 μM, respectively. However, the selectivity index reflects that the compounds 4g and 4o are more selective for hCA-II. The binding mode of these compounds within the active sites of bCA-II and hCA-II was investigated by structure-based molecular docking. The docking results are in complete agreement with the experimental findings.

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