Cyanine dyes derived inhibition of insulin fibrillization

The potential of novel cyanine dyes to inhibit the insulin amyloid formation was evaluated using thioflavin T fluorescence assay, quantum-chemical calculations, molecular docking and molecular dynamics simulations. According to the ability to suppress the insulin fibrillization under physiological conditions the examined compounds were found to follow the order: trimethines > pentamethines > monomethines > heptamethines. Of these, the trimethines 3-3 and 3-5, and pentamethines 5-3 and 5-9 almost completely prevented the protein aggregation by retarding both nucleation (except 3-3) and elongation processes. The quantum-chemical calculations revealed a complex relationship between the dye structure and its inhibitory effects. The molecular docking studies showed that most cyanines bind specifically to the L17 ladder of the B chain, located at the dry steric zipper of the insulin fibril protofilament, and form the stable complexes with the helices of the insulin monomer. The molecular dynamics simulations provided evidence for the increase of insulin helicity in the presence of cyanines. Collectively, the presented findings highlight two possible mechanisms by which cyanines can inhibit the insulin fibrillization: i) stabilization of the native protein structure followed by the retardation of the protein nucleation (all dyes); and ii) blocking the lateral extension of beta-sheets via the dye-protein stacking interactions (3-3, 3-5, 5-3, 5-9). Overall, the obtained results may prove of importance for the design of small molecules capable of preventing amyloid fibril formation by insulin and other proteins. (C) 2018 Elsevier B.V. All rights reserved.Peer reviewe

Maturation of the SARS-CoV-2 virus is regulated by dimerization of its main protease

SARS-CoV-2 main protease (Mpro) involved in COVID-19 is required for maturation of the virus and infection of host cells. The key question is how to block the activity of Mpro. By combining atomistic simulations with machine learning, we found that the enzyme regulates its own activity by a collective allosteric mechanism that involves dimerization and binding of a single substrate. At the core of the collective mechanism is the coupling between the catalytic site residues, H41 and C145, which direct the activity of Mpro dimer, and two salt bridges formed between R4 and E290 at the dimer interface. If these salt bridges are mutated, the activity of Mpro is blocked. The results suggest that dimerization of main proteases is a general mechanism to foster coronavirus proliferation, and propose a robust drug-based strategy that does not depend on the frequently mutating spike proteins at the viral envelope used to develop vaccines. (c) 2022 The Authors. Published by Elsevier B.V. on behalf of Research Network of Computational and Structural Biotechnology. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Peer reviewe

Cholesterol-recognition motifs in the transmembrane domain of the tyrosine kinase receptor family : The case of TRKB

Cholesterol is an essential constituent of cell membranes. The discovery of cholesterol-recognition amino acid consensus (CRAC) motif in proteins indicated a putative direct, non-covalent interaction between cholesterol and proteins. In the present study, we evaluated the presence of a CRAC motif and its inverted version (CARC) in the transmembrane region (TMR) of the tyrosine kinase receptor family (RTK) in several species using in silico methods. CRAC motifs were found across all species analyzed, while CARC was found only in vertebrates. The tropomyosin-related kinase B (TRKB), a member of the RTK family, through interaction with its endogenous ligand brain-derived neurotrophic factor (BDNF) is a core participant in the neuronal plasticity process and exhibits a CARC motif in its TMR. Upon identifying the conserved CARC motif in the TRKB, we performed molecular dynamics simulations of the mouse TRKB.TMR. The simulations indicated that cholesterol interaction with the TRKB CARC motif occurs mainly at the central Y433 residue. Our binding assay suggested a bell-shaped effect of cholesterol on BDNF interaction with TRKB receptors, and our results suggest that CARC/CRAC motifs may play a role in the function of the RTK family TMR.Peer reviewe

Molecular electrometer and binding of cations to phospholipid bilayers

Despite the vast amount of experimental and theoretical studies on the binding affinity of cations -especially the biologically relevant Na+ and Ca2+ - for phospholipid bilayers, there is no consensus in the literature. Here we show that by interpreting changes in the choline headgroup order parameters according to the 'molecular electrometer' concept [Seelig et al., Biochemistry, 1987, 26, 7535], one can directly compare the ion binding affinities between simulations and experiments. Our findings strongly support the view that in contrast to Ca2+ and other multivalent ions, Na+ and other monovalent ions (except Li+) do not specifically bind to phosphatidylcholine lipid bilayers at sub-molar concentrations. However, the Na+ binding affinity was overestimated by several molecular dynamics simulation models, resulting in artificially positively charged bilayers and exaggerated structural effects in the lipid headgroups. While qualitatively correct headgroup order parameter response was observed with Ca2+ binding in all the tested models, no model had sufficient quantitative accuracy to interpret the Ca2+: lipid stoichiometry or the induced atomistic resolution structural changes. All scientific contributions to this open collaboration work were made publicly, using nmrlipids. blogspot.fi as the main communication platform.Peer reviewe

Fluorescence study of the effect of the oxidized phospholipids on amyloid fibril formation by the apolipoprotein A-I N-terminal fragment

The effects of the oxidized phospholipids (oxPLs) on amyloid fibril formation by the apolipoprotein A-I variant 1-83/G26R have been investigated using Thioflavin T fluorescence assay. All types of the PoxnoPC assemblies (dispersions, micelles and lipid bilayer vesicles) induced retardation of amyloid nucleation and elongation and the enhancement of the 1-83/G26R fibrillization, although PazePC micelles completely prevented protein aggregation at low protein-to-lipid molar ratios. The ability of PazePC to inhibit 1-83/G26R aggregation was explained by the protein-lipid electrostatic interactions, which either stabilize the a-helical structure of the membrane-associated 1-83/G26R or facilitate the protein solubilization by the detergent micelles. (C) 2017 Elsevier B.V. All rights reserved.Peer reviewe

SMALL ANGLE X-RAY SCATTERING STUDY OF INSULIN FIBRILS

The small-angle X-ray scattering technique was employed to determine low-resolution 3D structure of insulin amyloid fibrils. This object is of particular interest since amyloid deposits of insulin causes insulin injection amyloidosis. Structural characterization of amyloid fibrils as a particular class of linear highly ordered protein aggregates is of utmost importance for deeper understanding of the molecular etiology of conformational diseases and development of effective therapeutic strategies. The small-angle X-ray scattering pattern analysis showed that the maximum dimension of the insulin fibril cross-section reaches 24±2.4 nm, while gyration radius of the cross-section is about 6 nm

Molecular basis of JAK2 activation in erythropoietin receptor and pathogenic JAK2 signaling

Janus kinase 2 (JAK2) mediates type I/II cytokine receptor signaling, but JAK2 is also activated by somatic mutations that cause hematological malignancies by mechanisms that are still incompletely understood. Quantitative superresolution microscopy (qSMLM) showed that erythropoietin receptor (EpoR) exists as monomers and dimer-izes upon Epo stimulation or through the predominant JAK2 pseudokinase domain mutations (V617F, K539L, and R683S). Crystallographic analysis complemented by kinase activity analysis and atomic-level simulations revealed distinct pseudokinase dimer interfaces and activation mechanisms for the mutants: JAK V617F activity is driven by dimerization, K539L involves both increased receptor dimerization and kinase activity, and R683S prevents autoinhibition and increases catalytic activity and drives JAK2 equilibrium toward activation state through a wild-type dimer interface. Artificial intelligence–guided modeling and simulations revealed that the pseudokinase mutations cause differences in the pathogenic full-length JAK2 dimers, particularly in the FERM-SH2 domains. A detailed molecular understanding of mutation-driven JAK2 hyperactivation may enable novel therapeutic approaches to selectively target pathogenic JAK2 signaling.Peer reviewe

Mechanistic Understanding from Molecular Dynamics in Pharmaceutical Research 2 : Lipid Membrane in Drug Design

We review the use of molecular dynamics (MD) simulation as a drug design tool in the context of the role that the lipid membrane can play in drug action, i.e., the interaction between candidate drug molecules and lipid membranes. In the standard “lock and key” paradigm, only the interaction between the drug and a specific active site of a specific protein is considered; the environment in which the drug acts is, from a biophysical perspective, far more complex than this. The possible mechanisms though which a drug can be designed to tinker with physiological processes are significantly broader than merely fitting to a single active site of a single protein. In this paper, we focus on the role of the lipid membrane, arguably the most important element outside the proteins themselves, as a case study. We discuss work that has been carried out, using MD simulation, concerning the transfection of drugs through membranes that act as biological barriers in the path of the drugs, the behavior of drug molecules within membranes, how their collective behavior can affect the structure and properties of the membrane and, finally, the role lipid membranes, to which the vast majority of drug target proteins are associated, can play in mediating the interaction between drug and target protein. This review paper is the second in a two-part series covering MD simulation as a tool in pharmaceutical research; both are designed as pedagogical review papers aimed at both pharmaceutical scientists interested in exploring how the tool of MD simulation can be applied to their research and computational scientists interested in exploring the possibility of a pharmaceutical context for their research

POPC_Ulmschneider_OPLS_Verlet_Group

<p>MD simulation trajectory and related files for fully hydrated POPC bilayer run with Verlet and Group schemes. The Ulmschneider force field for POPC was used with Gromacs 5.0.3 [1,2]. Conditions: T=298.15, 128 POPC molecules, 5120 tip3p waters. 200ns trajectory (preceded by 5ns NPT equillibration). Starting structure was obtained from CHARMM-GUI [3].</p> <p>This data is ran for the nmrlipids.blospot.fi project. More details from nmrlipids.blospot.fi and https://github.com/NMRLipids/nmrlipids.blogspot.fi</p> <p>[1] J.P. Ulmschneider & M.B. Ulmschneider, United Atom Lipid Parameters for Combination with the Optimized Potentials for Liquid Simulations All-Atom Force Field, JCTC 2009, 5(7), 1803–1813</p> <p>[2] http://lipidbook.bioch.ox.ac.uk/package/show/id/52.html</p> <p>[3] http://www.charmm-gui.org/</p

POPC_CHARMM36_CaCl2_1Mol

<p>The starting structure was constructed using the CHARMM-GUI Membrane Builder (http://www.charmm-gui.org/) online tool.</p> <p>All runs were performed with Gromacs 5.0.4 software package and CHARMM36 additive force field parameters obtained from CHARMM-GUI input files [1]. Conditions: T=303, 128 POPC molecules, 6400 tip3p waters (lipid/water 1:50), 100 Ca, 200 Cl. 200ns trajectory (preceded by standard CHARMM-GUI NPT equilibration) (2 files of 100ns).</p> <p>This data is ran for the nmrlipids.blospot.fi project. More details from nmrlipids.blospot.fi and https://github.com/NMRLipids/nmrlipids.blogspot.fi</p> <p>[1] CHARMM-GUI Input Generator for NAMD, GROMACS, AMBER, OpenMM, and CHARMM/OpenMM Simulations Using the CHARMM36 Additive Force Field,  J. Lee et al.<strong>,</strong> JCTC,<strong> </strong>DOI: 10.1021/acs.jctc.5b00935</p> <p> </p