Unraveling Binding Mechanism and Stability of Urease Inhibitors: A QM/MM MD Study.

Soil bacteria can produce urease, which catalyzes the hydrolysis of urea to ammonia (NH) and carbamate. A variety of urease inhibitors have been proposed to reduce NH volatilization by interfering with the urease activity. We report a quantum mechanics/molecular mechanics molecular dynamics (QM/MM MD) study on the mechanism employed for the inhibition of urease by three representative competitive inhibitors; namely, acetohydroxamic acid (AHA), hydroxyurea (HU), and -(-butyl)phosphorictriamide (NBPTO).

Development of serial X-ray fluorescence holography for radiation-sensitive protein crystals.

X-ray fluorescence holography (XFH) is a powerful atomic resolution technique capable of directly imaging the local atomic structure around atoms of a target element within a material. Although it is theoretically possible to use XFH to study the local structures of metal clusters in large protein crystals, the experiment has proven difficult to perform, especially on radiation-sensitive proteins. Here, the development of serial X-ray fluorescence holography to allow the direct recording of hologram patterns before the onset of radiation damage is reported.

Prediction of Protein Function from Tertiary Structure of the Active Site in Heme Proteins by Convolutional Neural Network.

Structure-function relationships in proteins have been one of the crucial scientific topics in recent research. Heme proteins have diverse and pivotal biological functions. Therefore, clarifying their structure-function correlation is significant to understand their functional mechanism and is informative for various fields of science.

Quantum chemical studies on hydrogen bonds in helical secondary structures.

Unlabelled: We present a brief review of our recent computational studies of hydrogen bonds (H-bonds) in helical secondary structures of proteins, α-helix and 3-helix, using a Negative Fragmentation Approach with density functional theory. We found that the depolarized electronic structures of the carbonyl oxygen of the th residue and the amide hydrogen of the ( + 4)th residue cause weaker H-bond in an α-helix than in an isolated H-bond. Our calculations showed that the H-bond energies in the 3-helix were also weaker than those of the isolated H-bonds.

Effects of Active-Center Reduction of Plant-Type Ferredoxin on Its Structure and Dynamics: Computational Analysis Using Molecular Dynamics Simulations.

"Plant-type" ferredoxins (Fds) in the thylakoid membranes of plants, algae, and cyanobacteria possess a single [2Fe-2S] cluster in active sites and mediate light-induced electron transfer from Photosystem I reaction centers to various Fd-dependent enzymes. Structural knowledge of plant-type Fds is relatively limited to static structures, and the detailed behavior of oxidized and reduced Fds has not been fully elucidated. It is important that the investigations of the effects of active-center reduction on the structures and dynamics for elucidating electron-transfer mechanisms.

Structures and mechanisms of actin ATP hydrolysis.

The major cytoskeleton protein actin undergoes cyclic transitions between the monomeric G-form and the filamentous F-form, which drive organelle transport and cell motility. This mechanical work is driven by the ATPase activity at the catalytic site in the F-form. For deeper understanding of the actin cellular functions, the reaction mechanism must be elucidated.

Elucidation of the Correlation between Heme Distortion and Tertiary Structure of the Heme-Binding Pocket Using a Convolutional Neural Network.

Heme proteins serve diverse and pivotal biological functions. Therefore, clarifying the mechanisms of these diverse functions of heme is a crucial scientific topic. Distortion of heme porphyrin is one of the key factors regulating the chemical properties of heme.

Depolarizing Effects in Hydrogen Bond Energy in 3-Helices Revealed by Quantum Chemical Analysis.

Hydrogen-bond (H-bond) energies in 3-helices of short alanine peptides were systematically examined by precise DFT calculations with the negative fragmentation approach (NFA), a modified method based on the molecular tailoring approach. The contribution of each H-bond was evaluated in detail from the 3-helical conformation of total energies (whole helical model, WH model), and the results were compared with the property of H-bond in α-helix from our previous study. The H-bond energies of the WH model exhibited tendencies different from those exhibited by the α-helix in that they depended on the helical position of the relevant H-bond pair.

Predicting Reaction Mechanisms for the Threonine-Residue Stereoinversion Catalyzed by a Dihydrogen Phosphate Ion.

The stereoinversion of amino acid residues in proteins is considered to trigger various age-related diseases. Serine (Ser) residues are relatively prone to stereoinversion. It is assumed that threonine (Thr) residues also undergo stereoinversion, which results in the formation of the d--Thr residue, by the same mechanisms as those for Ser-residue stereoinversion; however, d--Thr residues have not been detected in vivo.

QM/MM Molecular Dynamics Simulations Revealed Catalytic Mechanism of Urease.

Urease catalyzes the hydrolysis of urea to form ammonia and carbamate, inducing an overall pH increase that affects both human health and agriculture. Inhibition, mutagenesis, and kinetic studies have provided insights into its enzymatic role, but there have been debates on the substrate binding mode as well as the reaction mechanism. In the present study, we report quatum mechanics-only (QM-only) and quantum mechanics/molecular mechanics molecular dynamics (QM/MM MD) calculations on urease that mainly investigate the binding mode of urea and the mechanism of the urease-catalyzed hydrolysis reaction.

Development of a one-step analysis method for several amino acids using a microfluidic paper-based analytical device.

A one-step analysis method was developed for four types of amino acids using a microfluidic paper-based analytical device fabricated from chromatography filtration paper and laminate films. Aminoacyl-tRNA synthetase was used to detect each amino acid. The obtained laminated paper-based analytical device (LPAD) contained four enzymatic reaction areas.

Analysis of Fluctuation in the Heme-Binding Pocket and Heme Distortion in Hemoglobin and Myoglobin.

Heme is located in the active site of proteins and has diverse and important biological functions, such as electron transfer and oxygen transport and/or storage. The distortion of heme porphyrin is considered an important factor for the diverse functions of heme because it correlates with the physical properties of heme, such as oxygen affinity and redox potential. Therefore, clarification of the relationship between heme distortion and the protein environment is crucial in protein science.

Global Analysis of Heme Proteins Elucidates the Correlation between Heme Distortion and the Heme-Binding Pocket.

Heme proteins play diverse and important biological roles, from electron transfer and chemical catalysis to oxygen transport and/or storage. Although the distortion of heme porphyrin correlates with the physical properties of heme, such as the redox potential and oxygen affinity, the relationship between heme distortion and the heme protein environment is unclear. Here, we tested the hypothesis that the protein environment of the heme-binding pocket determines heme distortion (conformation).

Short-lived intermediate in NO generation by P450 NO reductase captured by time-resolved IR spectroscopy and XFEL crystallography.

Nitric oxide (NO) reductase from the fungus is a P450-type enzyme (P450nor) that catalyzes the reduction of NO to nitrous oxide (NO) in the global nitrogen cycle. In this enzymatic reaction, the heme-bound NO is activated by the direct hydride transfer from NADH to generate a short-lived intermediate ( ), a key state to promote N-N bond formation and N-O bond cleavage. This study applied time-resolved (TR) techniques in conjunction with photolabile-caged NO to gain direct experimental results for the characterization of the coordination and electronic structures of TR freeze-trap crystallography using an X-ray free electron laser (XFEL) reveals highly bent Fe-NO coordination in , with an elongated Fe-NO bond length (Fe-NO = 1.

PyDISH: database and analysis tools for heme porphyrin distortion in heme proteins.

Heme participates in a wide range of biological functions such as oxygen transport, electron transport, oxygen reduction, transcriptional regulation and so on. While the mechanism of each function has been investigated for many heme proteins, the origin of the diversity of the heme functions is still unclear and a crucial scientific issue. We have constructed a database of heme proteins, named Python-based database and analyzer for DIStortion of Heme porphyrin (PyDISH), which also contains some analysis tools.

Microfluidic Paper-Based Analytical Device for Histidine Determination.

A laminated paper-based analytical device (LPAD) for histidine detection was fabricated from a chromatography filtration paper and laminate films. Histidine recognition was effected by histidyl-tRNA synthetase (HisRS), and its detection was signaled colorimetrically based on the molybdenum blue reaction. The analytical conditions and detectable concentration range of histidine were examined.

Effects of a remote mutation from the contact paratope on the structure of CDR-H3 in the anti-HIV neutralizing antibody PG16.

PG16 is a broadly neutralizing antibody to the human immunodeficiency virus (HIV). A crystal structure of PG16 revealed that the unusually long 28-residue complementarity determining region (CDR) H3 forms a unique subdomain, referred to as a "hammerhead", that directly contacts the antigen. The hammerhead apparently governs the function of PG16 while a previous experimental assay showed that the mutation of Tyr to Ala, which does not directly contact the antigen, decreased the neutralization ability of PG16.

Hydrogen bond donors and acceptors are generally depolarized in α-helices as revealed by a molecular tailoring approach.

Hydrogen-bond (H-bond) interaction energies in α-helices of short alanine peptides were systematically examined by precise density functional theory calculations, followed by a molecular tailoring approach. The contribution of each H-bond interaction in α-helices was estimated in detail from the entire conformation energies, and the results were compared with those in the minimal H-bond models, in which only H-bond donors and acceptors exist with the capping methyl groups. The former interaction energies were always significantly weaker than the latter energies, when the same geometries of the H-bond donors and acceptors were applied.

Quantitative Assessment of rPM6 for Fluorine- and Chlorine-Containing Metal Complexes: Comparison with Experimental, First-Principles, and Other Semiempirical Results.

We report a reparameterization of PM6 parameters for fluorine and chlorine using our training set containing transition metal complexes. Spin unrestricted calculations with the resulting rPM6 (UrPM6) were examined quantitatively using two test sets: (i) the description of magnetic interactions in 25 dinuclear metal complexes and (ii) the prediction of barrier heights and reaction energies for epoxidation and fluorination reactions catalyzed by high-valent manganese-oxo species. The conventional UPM6 and UPM7 methods were also evaluated for comparison on the basis of either experimental or computational (the UB3LYP/SVP level) outcomes.

Zn-Binding to the Voltage-Gated Proton Channel Hv1/VSOP.

The voltage-gated proton channel (Hv1/VSOP) is inhibited by Zn, of which the binding site is located in the extracellular region. We utilized attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy to examine the coordination structure by monitoring protein structural changes induced by Zn-binding. The Zn-induced difference ATR-FTIR spectra of Hv1 showed IR features that can be assigned to the histidine C5-N1 and carboxylate-COO stretches as well as amide I changes likely in α-helical peptide bonds.

Density functional study of porphyrin distortion effects on redox potential of heme.

Heme is involved in various biochemical roles in hemoproteins. In the present study, the effect of heme distortion on the redox potential was systematically investigated with density functional calculations. We focused on the ruffled and saddled distortions of heme, which correspond to the two lowest-frequency normal modes.

J-shaped stress-strain diagram of collagen fibers: Frame tension of triangulated surfaces with fixed boundaries.

We present Monte Carlo data of the stress-strain diagrams obtained using two different triangulated surface models. The first is the canonical surface model of Helfrich and Polyakov (HP), and the second is a Finsler geometry (FG) model. The shape of the experimentally observed stress-strain diagram is called J-shaped.