scholarly journals Photolabelling of Salmonella typhimurium LT2 sialidase. Identification of a peptide with a predicted structural similarity to the active sites of influenza-virus sialidases

1992 ◽  
Vol 285 (3) ◽  
pp. 957-964 ◽  
Author(s):  
T G Warner ◽  
R Harris ◽  
R McDowell ◽  
E R Vimr
Keyword(s):  
Salmonella Typhimurium ◽  
Active Site ◽  
Influenza A ◽  
Active Sites ◽  
Enzyme Inhibitors ◽  
Structural Similarity ◽  
Competitive Inhibitor ◽  
Beta Sheets ◽  
Sialidase Inhibitor ◽  
Active Site Cavity

The sialidase from Salmonella typhimurium LT2 was characterized by using photoaffinity-labelling techniques. The well-known sialidase inhibitor 5-acetamido-2,6-anhydro-3,5-dideoxy-D-glycero-D-galacto-non- 2-enonic acid (Neu5Ac2en) was modified to contain an amino group at C-9, which permitted the incorporation of 4-azidosalicylic acid in amide linkage at this position. Labelling of the purified protein with the radioactive (125I) photoprobe was determined to be highly specific for a region within the active-site cavity. This conclusion was based on the observation that the competitive inhibitor Neu5Ac2en in the photolysis mixture prevented labelling of the protein. In contrast, compounds with structural and chemical features similar to the probe and Neu5Ac2en, but which were not competitive enzyme inhibitors, did not affect the photolabelling of the protein. The peptide interacting with the probe was identified by CNBr treatment of the labelled protein, followed by N-terminal sequence analysis. Inspection of the primary structure of the protein, predicted from the cloned structural gene for the sialidase [Hoyer, Hamilton, Steenbergen & Vimr (1992) Mol. Microbiol. 6, 873-884] revealed that the label was incorporated into a 9.6 kDa fragment situated within the terminal third of the molecule near the C-terminal end. Secondary-structural predictions using the Garnier-Robson algorithm [Garnier, Osguthorpe & Robson (1978) J. Mol. Biol. 120, 97-120] of the labelled peptide revealed a structural similarity to the active site of influenza-A- and Sendai-HN-virus sialidases with a repetitive series of alternating beta-sheets connected with loops.

scholarly journals Structural insights into enzymatic [4+2] aza-cycloaddition in thiopeptide antibiotic biosynthesis

2017 ◽  
Vol 114 (49) ◽  
pp. 12928-12933 ◽  
Author(s):  
Dillon P. Cogan ◽  
Graham A. Hudson ◽  
Zhengan Zhang ◽  
Taras V. Pogorelov ◽  
Wilfred A. van der Donk ◽  
...  
Keyword(s):  
Protein Design ◽  
Active Site ◽  
Active Sites ◽  
De Novo ◽  
Core Protein ◽  
Cycloaddition Reaction ◽  
Structural Similarity ◽  
Antibiotic Biosynthesis ◽  
Binding Studies ◽  
Nitrogenous Heterocycle

The [4+2] cycloaddition reaction is an enabling transformation in modern synthetic organic chemistry, but there are only limited examples of dedicated natural enzymes that can catalyze this transformation. Thiopeptides (or more formally thiazolyl peptides) are a class of thiazole-containing, highly modified, macrocyclic secondary metabolites made from ribosomally synthesized precursor peptides. The characteristic feature of these natural products is a six-membered nitrogenous heterocycle that is assembled via a formal [4+2] cycloaddition between two dehydroalanine (Dha) residues. This heteroannulation is entirely contingent on enzyme activity, although the mechanism of the requisite pyridine/dehydropiperidine synthase remains to be elucidated. The unusual aza-cylic product is distinct from the more common carbocyclic products of synthetic and biosynthetic [4+2] cycloaddition reactions. To elucidate the mechanism of cycloaddition, we have determined atomic resolution structures of the pyridine synthases involved in the biosynthesis of the thiopeptides thiomuracin (TbtD) and GE2270A (PbtD), in complex with substrates and product analogs. Structure-guided biochemical, mutational, computational, and binding studies elucidate active-site features that explain how orthologs can generate rigid macrocyclic scaffolds of different sizes. Notably, the pyridine synthases show structural similarity to the elimination domain of lanthipeptide dehydratases, wherein insertions of secondary structural elements result in the formation of a distinct active site that catalyzes different chemistry. Comparative analysis identifies other catalysts that contain a shared core protein fold but whose active sites are located in entirely different regions, illustrating a principle predicted from efforts in de novo protein design.

scholarly journals Carbonic Anhydrase Activators. Part 191 Spectroscopic and Kinetic Investigations for the Interaction of Isozymes I and II With Primary Amines

1997 ◽  
Vol 4 (4) ◽  
pp. 221-227 ◽  
Author(s):  
Fabrizio Briganti ◽  
Andrea Scozzafava ◽  
Claudiu T. Supuran
Keyword(s):  
Carbonic Anhydrase ◽  
Active Site ◽  
Metal Ion ◽  
Competitive Inhibitor ◽  
The Other ◽  
Primary Amines ◽  
Hydrophobic Pocket ◽  
X Ray ◽  
Active Site Cavity ◽  
Kinetic Investigations

The interactions of Zn(II)- and Co(II)-substituted carbonic anhydrase (CA) isozymes I and II with amine type activators such as histamine, serotonin, phenetylamine dopamine and benzylhydrazine have been investigated kinetically, and spectroscopically. All of such activators are of the non-competitive type towards CO2 hydration and 4-nitrophenylacetate hydrolysis for both human isozymes (HCA I and HCA II). The electronic spectra of the adducts of Co(II)CA with amine activators are similar to the spectrum of the previously reported Co(II)CAII-phenol adduct, the only known competitive inhibitor towards CO2 hydration, where the phenol molecule binds into the hydrophobic pocket of the active site. This is a direct spectroscopic evidence that the activator molecules bind within the active site, but not directly to the metal ion. Recent X-ray crystallographic data for the adduct of HCA II with histamine show that the activator molecule is bound at the entrance of the active site cavity, near to residues His 64, Asn 62 and Gln 92, where actively aids in shuttling protons between the active site and the environment. Similar arrangements probably occur for the other activators reported in the present paper.

scholarly journals Active-Site Models of Streptococcus pyogenes Cas9 in DNA Cleavage State

2021 ◽  
Vol 8 ◽  
Author(s):  
Honghai Tang ◽  
Hui Yuan ◽  
Wenhao Du ◽  
Gan Li ◽  
Dongmei Xue ◽  
...  
Keyword(s):  
Active Site ◽  
Dna Cleavage ◽  
Metal Ion ◽  
Active Sites ◽  
Structural Similarity ◽  
Atomic Model ◽  
Nucleophilic Attack ◽  
Target Dna ◽  
Coordinated Water ◽  
Dna Complex

CRISPR-Cas9 is a powerful tool for target genome editing in living cells. Significant advances have been made to understand how this system cleaves target DNA. HNH is a nuclease domain, which shares structural similarity with the HNH endonuclease characterzied by a beta-beta-alpha-metal fold. Therefore, based on one- and two-metal-ion mechanisms, homology modeling and molecular dynamics (MD) simulation are suitable tools for building an atomic model of Cas9 in the DNA cleavage state. Here, by modeling and MD, we presented an atomic model of SpCas9–sgRNA–DNA complex with the cleavage state. This model shows that the HNH and RuvC conformations resemble their DNA cleavage state where the active-sites in the complex coordinate with DNA, Mg2+ ions, and water. Among them, residues D10, E762, H983, and D986 locate at the first shell of the RuvC active-site and interact with the ions directly, residues H982 or/and H985 are general (Lewis) bases, and the coordinated water is located at the positions for nucleophilic attack of the scissile phosphate. Meanwhile, this catalytic model led us to engineer a new SpCas9 variant (SpCas9-H982A + H983D) with reduced off-target effects. Thus, our study provided new mechanistic insights into the CRISPR-Cas9 system in the DNA cleavage state and offered useful guidance for engineering new CRISPR-Cas9 editing systems with improved specificity.

scholarly journals The electrostatic fields in the active-site clefts of actinidin and papain

1988 ◽  
Vol 254 (1) ◽  
pp. 235-238 ◽  
Author(s):  
R W Pickersgill ◽  
P W Goodenough ◽  
I G Sumner ◽  
M E Collins
Keyword(s):  
Active Site ◽  
Active Sites ◽  
Structural Similarity ◽  
Cysteine Residue ◽  
Site Directed Mutagenesis ◽  
Activity Profile ◽  
Active Site Cysteine ◽  
Electrostatic Fields ◽  
Imidazolium Ion ◽  
Active Site Cysteine Residue

The active sites of actinidin (EC 3.4.22.14) and papain (EC 3.4.22.2) display different reactivity characteristics to probes targeted at the active-site cysteine residue despite the close structural similarity of their active sites. The calculated electrostatic fields in the active-site clefts of actinidin and papain differ significantly and may explain the reactivity characteristics of these enzymes. Calculation of electrostatic potential also focuses attention on the electrostatic properties that govern formation of the active-site thiolate-imidazolium ion-pair. These calculations will guide the modification of the pH-activity profile of the cysteine proteinases by site-directed mutagenesis.

Structural basis for the extended substrate spectrum of AmpC BER and structure-guided discovery of the inhibition activity of citrate against the class C β-lactamases AmpC BER and CMY-10

2016 ◽  
Vol 72 (8) ◽  
pp. 976-985 ◽  
Author(s):  
Jung-Hyun Na ◽  
Sun-Shin Cha
Keyword(s):  
Active Site ◽  
Active Sites ◽  
Competitive Inhibitor ◽  
Structural Basis ◽  
Active Site Residues ◽  
Weakly Bound ◽  
Primary Metabolite ◽  
Operative Strategy ◽  
Class C ◽  
Substrate Spectrum

AmpC BER is an extended substrate spectrum class C β-lactamase with a two-amino-acid insertion in the R2 loop compared with AmpC EC2. The crystal structures of AmpC BER (S64A mutant) and AmpC EC2 were determined. Structural comparison of the two proteins revealed that the insertion increases the conformational flexibility of the R2 loop. Two citrate molecules originating from the crystallization solution were observed in the active site of the S64A mutant. One citrate molecule makes extensive interactions with active-site residues that are highly conserved among class C β-lactamases, whereas the other one is weakly bound. Based on this structural observation, it is demonstrated that citrate, a primary metabolite that is widely used as a food additive, is a competitive inhibitor of two class C β-lactamases (AmpC BER and CMY-10). Consequently, the data indicate enhancement of the flexibility of the R2 loop as an operative strategy for molecular evolution of extended-spectrum class C β-lactamases, and also suggest that the citrate scaffold is recognized by the active sites of class C β-lactamases.

scholarly journals Computational Evaluation of 2-Phenyl-4H-chromen-4-one Analogues as Antihistamines: Potential HistamineN-Methyltransferase (HMT) Inhibitors

2009 ◽  
Vol 6 (4) ◽  
pp. 1009-1016
Author(s):  
Shikha S. Dave ◽  
Anjali M. Rahatgaonkar
Keyword(s):  
Binding Energy ◽  
Active Sites ◽  
Competitive Inhibitor ◽  
Binding Energies ◽  
Human Beings ◽  
High Concentration ◽  
Major Pathway ◽  
Methyl Transferase ◽  
Computational Evaluation ◽  
Active Site Cavity

Abnormal release of histamine, which is present in relatively high concentration in the lungs, causes serious allergic vasoconstriction and anaphylactic manifestation in human beings. In mammals, a major pathway of histamine metabolism in the lungs is mediated by histamineN-methyl transferase (HMT) and diamine oxidase. The need to design a strategy of mechanistic computational evaluation of protein-ligand affinityi.e. HMT- 2-phenyl-4H-chromen-4-ones, protein complex binding energy has been established. A library of synthesized 2-phenyl-4H-chromen-4-ones was docked into the active site cavity of target protein, HMT (Pdb: 2aot). The high-resolution crystal structure of HMT complex with the competitive inhibitorN[2 (benzhydryloxy)ethyl]N N-Dimethylamine (Diphenhydramine) revealed a protein with a highly confined binding region that could be targeted in the design of specific anti-histamines. The validation of docking programme by Potential Mean Force was compared with binding energy results of known ligands in the active sites of HMT, diphenhydramine / benadryl, promethazine, cyproheptadine, trimeton / aviletc. All the synthesized chromone derivatives showed comparable negative binding energies pointing towards the fact that these molecules could be potent antihistamines.

Catalytic Resonance Theory: Parallel Reaction Pathway Control

2019 ◽  
Author(s):  
M. Alexander Ardagh ◽  
Manish Shetty ◽  
Anatoliy Kuznetsov ◽  
Qi Zhang ◽  
Phillip Christopher ◽  
...  
Keyword(s):  
Chemical Reactions ◽  
Active Site ◽  
Active Sites ◽  
Reaction Pathway ◽  
Control Strategies ◽  
Oscillation Amplitude ◽  
Catalytic Performance ◽  
Parallel Reaction ◽  
Resonance Theory ◽  
Static Conditions

Catalytic enhancement of chemical reactions via heterogeneous materials occurs through stabilization of transition states at designed active sites, but dramatically greater rate acceleration on that same active site is achieved when the surface intermediates oscillate in binding energy. The applied oscillation amplitude and frequency can accelerate reactions orders of magnitude above the catalytic rates of static systems, provided the active site dynamics are tuned to the natural frequencies of the surface chemistry. In this work, differences in the characteristics of parallel reactions are exploited via selective application of active site dynamics (0 < ΔU < 1.0 eV amplitude, 10<sup>-6</sup> < f < 10<sup>4</sup> Hz frequency) to control the extent of competing reactions occurring on the shared catalytic surface. Simulation of multiple parallel reaction systems with broad range of variation in chemical parameters revealed that parallel chemistries are highly tunable in selectivity between either pure product, even when specific products are not selectively produced under static conditions. Two mechanisms leading to dynamic selectivity control were identified: (i) surface thermodynamic control of one product species under strong binding conditions, or (ii) catalytic resonance of the kinetics of one reaction over the other. These dynamic parallel pathway control strategies applied to a host of chemical conditions indicate significant potential for improving the catalytic performance of many important industrial chemical reactions beyond their existing static performance.

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