scholarly journals C-mannosylation supports folding and enhances stability of thrombospondin repeats

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Aleksandra Shcherbakova ◽  
Matthias Preller ◽  
Manuel H Taft ◽  
Jordi Pujols ◽  
Salvador Ventura ◽  
...  
Keyword(s):  
Significant Proportion ◽  
Experimental Studies ◽  
Intramolecular Hydrogen Bonding ◽  
Tryptophan Residues ◽  
Disulfide Bridging ◽  
Dynamics Simulations ◽  
Intramolecular Hydrogen ◽  
Thrombospondin Type 1 Repeats

Previous studies demonstrated importance of C-mannosylation for efficient protein secretion. To study its impact on protein folding and stability, we analyzed both C-mannosylated and non-C-mannosylated thrombospondin type 1 repeats (TSRs) of netrin receptor UNC-5. In absence of C-mannosylation, UNC-5 TSRs could only be obtained at low temperature and a significant proportion displayed incorrect intermolecular disulfide bridging, which was hardly observed when C-mannosylated. Glycosylated TSRs exhibited higher resistance to thermal and reductive denaturation processes, and the presence of C-mannoses promoted the oxidative folding of a reduced and denatured TSR in vitro. Molecular dynamics simulations supported the experimental studies and showed that C-mannoses can be involved in intramolecular hydrogen bonding and limit the flexibility of the TSR tryptophan-arginine ladder. We propose that in the endoplasmic reticulum folding process, C-mannoses orient the underlying tryptophan residues and facilitate the formation of the tryptophan-arginine ladder, thereby influencing the positioning of cysteines and disulfide bridging.

scholarly journals Antiglycation potential of Indigoferin a, Indigoferin B and Indigoferin C natural products from Indigofera heterantha Brandis

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Ayesha Khan ◽  
Ajmal Khan ◽  
Manzoor Ahmad ◽  
Mumtaz Ali ◽  
Umar Farooq ◽  
...  
Keyword(s):  
Natural Products ◽  
Diabetic Complications ◽  
Inhibitory Activity ◽  
Chemical Constituents ◽  
Intramolecular Hydrogen Bonding ◽  
Glycation End Products ◽  
End Products ◽  
Serious Disease ◽  
Intramolecular Hydrogen

Abstract Background Diabetes is a long-lasting and serious disease that effect in worldwide individual lives, families, and societies. Hyperglycemia of diabetes mellitus produced Advance Glycation End Products that are associated with diabetic complications like neuropathy, nephropathy, retinopathy, and cardiovascular diseases. Methods In this study, the natural products isolated from of Indigofera heterantha Brandis, Indigoferin A (S1), Indigoferin B (S2) and Indigoferin C (S3) were evaluated for their in vitro antiglycation activity. Results The compounds exhibited a significant inhibitory activity against the formation of Advanced Glycation End-Products with IC50 values of 674.25 ± 3.2 μM, 407.03 ± 4.7 μM and 726.41 ± 2.1 μM, respectively. Here, important structure-activity relationship was observed, when the intramolecular hydrogen bonding interactions suppressed the antiglycation activity of compound S3. Thus, the study clearly demonstrates that the number and the position of substituents act as an assisting factor and directly influence the inhibitory activity of the natural product by altering the sugar or protein binding affinity. Conclusions This study explain first time the antiglycation inhibitory ability of chemical constituents isolated from I. heterantha and can be used for above late diabetic complications.

scholarly journals Incorporation of an intramolecular hydrogen bonding motif in the side chain of antimalarial benzimidazoles

MedChemComm ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 450-455 ◽  
Author(s):  
Henrietta D. Attram ◽  
Sergio Wittlin ◽  
Kelly Chibale
Keyword(s):  
Plasmodium Falciparum ◽  
Hydrogen Bonding ◽  
Malaria Parasite ◽  
Intramolecular Hydrogen Bonding ◽  
Side Chain ◽  
Drug Resistant ◽  
Human Malaria Parasite ◽  
Human Malaria ◽  
Intramolecular Hydrogen

Analogues of a novel class of benzimidazoles with an intramolecular hydrogen bonding motif have been synthesized and evaluated in vitro for their antiplasmodium activity against chloroquine-sensitive (NF54) and multi-drug resistant (K1) strains of the human malaria parasite Plasmodium falciparum.

scholarly journals C-Mannosylation of Toxoplasma gondii proteins promotes attachment to host cells and parasite virulence

2019 ◽  
Vol 295 (4) ◽  
pp. 1066-1076 ◽  
Author(s):  
Andreia Albuquerque-Wendt ◽  
Damien Jacot ◽  
Nicolas Dos Santos Pacheco ◽  
Carla Seegers ◽  
Patricia Zarnovican ◽  
...  
Keyword(s):  
Toxoplasma Gondii ◽  
Protective Immunity ◽  
Host Cells ◽  
Apicomplexan Parasites ◽  
Tryptophan Residues ◽  
Parasite Survival ◽  
Parasite Motility ◽  
Parasite Egress ◽  
Thrombospondin Type 1 Repeats

C-Mannosylation is a common modification of thrombospondin type 1 repeats present in metazoans and recently identified also in apicomplexan parasites. This glycosylation is mediated by enzymes of the DPY19 family that transfer α-mannoses to tryptophan residues in the sequence WX2WX2C, which is part of the structurally essential tryptophan ladder. Here, deletion of the dpy19 gene in the parasite Toxoplasma gondii abolished C-mannosyltransferase activity and reduced levels of the micronemal protein MIC2. The loss of C-mannosyltransferase activity was associated with weakened parasite adhesion to host cells and with reduced parasite motility, host cell invasion, and parasite egress. Interestingly, the C-mannosyltransferase–deficient Δdpy19 parasites were strongly attenuated in virulence and induced protective immunity in mice. This parasite attenuation could not simply be explained by the decreased MIC2 level and strongly suggests that absence of C-mannosyltransferase activity leads to an insufficient level of additional proteins. In summary, our results indicate that T. gondii C-mannosyltransferase DPY19 is not essential for parasite survival, but is important for adhesion, motility, and virulence.

Synthesis, molecular packing and anti-cholinesterase activity of some new C-2 N-substituted anthranilamide derivatives

2019 ◽  
Vol 234 (9) ◽  
pp. 605-611 ◽  
Author(s):  
Muhammad Sarfraz ◽  
Nargis Sultana ◽  
Muhammad Ilyas Tariq ◽  
Masood Parvez
Keyword(s):  
Hydrogen Bonding ◽  
Cholinesterase Activity ◽  
Intramolecular Hydrogen Bonding ◽  
Pharmacokinetic Profile ◽  
Intermolecular Hydrogen Bonds ◽  
Standard Drug ◽  
X Ray ◽  
Hydrogen Bonding Interactions ◽  
Intramolecular Hydrogen

Abstract Synthesis of C-2 N-substituted anthranilamide derivatives was carried out in a straight forward manner, utilizing 2-aminobenzamide and benzyl chloride as starting materials. Their crystal structures have been established by single crystal X-ray crystallographic method. In the molecules of 2-benzylamino-benzamide (3a), intramolecular hydrogen bonding b/w O atom and proton of –NH and classical intermolecular hydrogen bonding of the type N–H · · · O forming eight membered rings in R42(8) pattern. In both molecules of 2-(dibenzylamino)benzamide (3b), unlike the molecule in 3a, each H atoms is pointed towards N atom causing intramolecular hydrogen bonding interactions, resulting in S(6) motifs. However, it is interesting to note that both molecules in 3b are lying about inversion centres and form dimers in R42(8) motifs; the two dimers are linked via non-classical intermolecular hydrogen bonds C–H · · · O resulting in clusters of four molecules in the structure. In vitro assay results revealed that molecule 3b with IC50 values of 3.8 ± 0.08 μM (AChE) and 17.6 ± 1.10 μM (BChE) possessed better cholinesterase (AChE and BChE) inhibition potential as compared to standard drug galantamine. Preliminary in silico studies showed that more biological active derivatives were also having good pharmacokinetic profile with no AMES toxicity and carcinogenicity.

scholarly journals Influence of water and enzyme SpnF on the dynamics and energetics of the ambimodal [6+4]/[4+2] cycloaddition

2018 ◽  
Vol 115 (5) ◽  
pp. E848-E855 ◽  
Author(s):  
Zhongyue Yang ◽  
Song Yang ◽  
Peiyuan Yu ◽  
Yanwei Li ◽  
Charles Doubleday ◽  
...  
Keyword(s):  
Transition State ◽  
Isotope Effects ◽  
Phase 1 ◽  
Intramolecular Hydrogen Bonding ◽  
Diels Alder ◽  
Uncatalyzed Reaction ◽  
Dynamics Simulations ◽  
Enzyme Catalyzed Reactions ◽  
Intramolecular Hydrogen ◽  
Alder Adduct

SpnF is the first monofunctional Diels–Alder/[6+4]-ase that catalyzes a reaction leading to both Diels–Alder and [6+4] adducts through a single transition state. The environment-perturbed transition-state sampling method has been developed to calculate free energies, kinetic isotope effects, and quasi-classical reaction trajectories of enzyme-catalyzed reactions and the uncatalyzed reaction in water. Energetics calculated in this way reproduce the experiment and show that the normal Diels–Alder transition state is stabilized by H bonds with water molecules, while the ambimodal transition state is favored in the enzyme SpnF by both intramolecular hydrogen bonding and hydrophobic binding. Molecular dynamics simulations show that trajectories passing through the ambimodal transition state bifurcate to the [6+4] adduct and the Diels–Alder adduct with a ratio of 1:1 in the gas phase, 1:1.6 in water, and 1:11 in the enzyme. This example shows how an enzyme acts on a vibrational time scale to steer post-transition state trajectories toward the Diels–Alder adduct.

scholarly journals Influence of Hyperglycemia and Diabetes on Cardioprotection by Humoral Factors Released after Remote Ischemic Preconditioning (RIPC)

2021 ◽  
Vol 22 (16) ◽  
pp. 8880
Author(s):  
Carolin Torregroza ◽  
Lara Gnaegy ◽  
Annika Raupach ◽  
Martin Stroethoff ◽  
Katharina Feige ◽  
...  
Keyword(s):  
Infarct Size ◽  
Ischemic Preconditioning ◽  
Ischemia Reperfusion ◽  
Experimental Studies ◽  
Limb Ischemia ◽  
Remote Ischemic Preconditioning ◽  
Humoral Factors

Remote ischemic preconditioning (RIPC) protects hearts from ischemia–reperfusion (I/R) injury in experimental studies; however, clinical RIPC trials were unsatisfactory. This discrepancy could be caused by a loss of cardioprotection due to comorbidities in patients, including diabetes mellitus (DM) and hyperglycemia (HG). RIPC is discussed to confer protective properties by release of different humoral factors activating cardioprotective signaling cascades. Therefore, we investigated whether DM type 1 and/or HG (1) inhibit the release of humoral factors after RIPC and/or (2) block the cardioprotective effect directly at the myocardium. Experiments were performed on male Wistar rats. Animals in part 1 of the study were either healthy normoglycemic (NG), type 1 diabetic (DM1), or hyperglycemic (HG). RIPC was implemented by four cycles of 5 min bilateral hind-limb ischemia/reperfusion. Control (Con) animals were not treated. Blood plasma taken in vivo was further investigated in isolated rat hearts in vitro. Plasma from diseased animals (DM1 or HG) was administered onto healthy (NG) hearts for 10 min before 33 min of global ischemia and 60 min of reperfusion. Part 2 of the study was performed vice versa—plasma taken in vivo, with or without RIPC, from healthy rats was transferred to DM1 and HG hearts in vitro. Infarct size was determined by TTC staining. Part 1: RIPC plasma from NG (NG Con: 49 ± 8% vs. NG RIPC 29 ± 6%; p < 0.05) and DM1 animals (DM1 Con: 47 ± 7% vs. DM1 RIPC: 38 ± 7%; p < 0.05) reduced infarct size. Interestingly, transfer of HG plasma showed comparable infarct sizes independent of prior treatment (HG Con: 34 ± 9% vs. HG RIPC 35 ± 9%; ns). Part 2: No infarct size reduction was detectable when transferring RIPC plasma from healthy rats to DM1 (DM1 Con: 54 ± 13% vs. DM1 RIPC 53 ± 10%; ns) or HG hearts (HG Con: 60 ± 16% vs. HG RIPC 53 ± 14%; ns). These results suggest that: (1) RIPC under NG and DM1 induces the release of humoral factors with cardioprotective impact, (2) HG plasma might own cardioprotective properties, and (3) RIPC does not confer cardioprotection in DM1 and HG myocardium.

In vitro interaction and computational studies of glycosylated photosensitizers with plasma proteins

2019 ◽  
Vol 23 (04n05) ◽  
pp. 437-452 ◽  
Author(s):  
Diana Samaroo ◽  
Mai Zahran ◽  
Andrew C. Wills ◽  
Johnny Guevara ◽  
Alexandra Tatonetti
Keyword(s):  
Serum Albumin ◽  
Plasma Proteins ◽  
Experimental Studies ◽  
Fluorescence Emission ◽  
Strong Interactions ◽  
Tryptophan Residue ◽  
Dynamics Simulations ◽  
In Vitro Interaction ◽  
Computational Molecular Docking

A series of glycosylated photosensitizers (porphyrin, chlorin, and isobacteriochlorin) in the presence of plasma proteins: bovine serum albumin (BSA) and human serum albumin (HSA), were investigated in a buffer at pH 7.4, using ultraviolet-visible (UV-vis) absorption and fluorescence spectroscopies. Due to the excitation of the tryptophan residue of BSA and HSA, its fluorescence emission was monitored around 340 nm. During each titration experiment and with each addition of the corresponding glycosylated photosensitizer, there was a concentration-dependent quenching of the intrinsic fluorescence of BSA and HSA. Using Stern–Volmer and double logarithmic plots we determined that fluorescence quenching was static for all molecules. We calculated the average binding constant for BSA and HSA for each porphyrin-type compound. To support our experimental studies, computational molecular docking and molecular dynamics simulations were used to identify the binding sites and binding poses of the each of the glycosylated photosensitizers onto BSA and HSA. The three compounds are binding to the Hemin site located in the subdomain IB of BSA forming strong interactions with Trp134, while they are binding to the subdomain IIA of HSA close to the Sudlow’s site I, and interacting with Trp214.

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