Database Of Complexes Research Articles

MFIB 2.0: a major update of the database of protein complexes formed by mutual folding of the constituting protein chains.

While the majority of proteins with available structures are able to fold independently and mediate interactions only after acquiring their folded state, a subset of the known protein complexes contains protein chains that are intrinsically disordered in isolation. The Mutual Folding Induced by Binding (MFIB) database collects and classifies protein complexes, wherein all constituent protein chains would be unstable/disordered in isolation but fold into a well-defined 3D complex structure upon binding. This phenomenon is often termed as cooperative folding and binding or mutual synergistic folding (MSF). Here we present a major update to the database: we collected and annotated hundreds of new protein complexes fulfilling the criteria of MSF, leading to an almost six-fold increase in the size of the database. Many novel features have also been introduced, such as clustering of the complexes based on structural similarity and domain types, assigning different evidence levels to each entry and adding the evidence coverage label that allowed us to include complexes of multi(sub)domain monomers with partial MSF. The MFIB 2.0 database is available at https://mfib.pbrg.hu.

ThermoPCD: a database of molecular dynamics trajectories of antibody-antigen complexes at physiologic and fever-range temperatures.

Progression of various cancers and autoimmune diseases is associated with changes in systemic or local tissue temperatures, which may impact current therapies. The role of fever and acute inflammation-range temperatures on the stability and activity of antibodies relevant for cancers and autoimmunity is unknown. To produce molecular dynamics (MD) trajectories of immune complexes at relevant temperatures, we used the Research Collaboratory for Structural Bioinformatics (RCSB) database to identify 50 antibody:antigen complexes of interest, in addition to single antibodies and antigens, and deployed Groningen Machine for Chemical Simulations (GROMACS) to prepare and run the structures at different temperatures for 100-500ns, in single or multiple random seeds. MD trajectories are freely available. Processed data include Protein Data Bank outputs for all files obtained every 50ns, and free binding energy calculations for some of the immune complexes. Protocols for using the data are also available. Individual datasets contain unique DOIs. We created a web interface, ThermoPCD, as a platform to explore the data. The outputs of ThermoPCD allow the users to relate thermally-dependent changes in epitopes:paratopes interfaces to their free binding energies, or against own experimentally derived binding affinities. ThermoPCD is a free to use database of immune complexes' trajectories at different temperatures that does not require registration and allows for all the data to be available for download. Database URL: https://sites.google.com/view/thermopcd/home.

Automated prediction of ground state spin for transition metal complexes.

Exploiting crystallographic data repositories for large-scale quantum chemical computations requires the rapid and accurate extraction of the molecular structure, charge and spin from the crystallographic information file. Here, we develop a general approach to assign the ground state spin of transition metal complexes, in complement to our previous efforts on determining metal oxidation states and bond order within the cell2mol software. Starting from a database of 31k transition metal complexes extracted from the Cambridge Structural Database with cell2mol, we construct the TM-GSspin dataset, which contains 2063 mononuclear first row transition metal complexes and their computed ground state spins. TM-GSspin is highly diverse in terms of metals, metal oxidation states, coordination geometries, and coordination sphere compositions. Based on TM-GSspin, we identify correlations between structural and electronic features of the complexes and their ground state spins to develop a rule-based spin state assignment model. Leveraging this knowledge, we construct interpretable descriptors and build a statistical model achieving 98% cross-validated accuracy in predicting the ground state spin across the board. Our approach provides a practical way to determine the ground state spin of transition metal complexes directly from crystal structures without additional computations, thus enabling the automated use of crystallographic data for large-scale computations involving transition metal complexes.

EpiFactors 2022: expansion and enhancement of a curated database of human epigenetic factors and complexes.

We present an update of EpiFactors, a manually curated database providing information about epigenetic regulators, their complexes, targets, and products which is openly accessible at http://epifactors.autosome.org. An updated version of the EpiFactors contains information on 902 proteins, including 101 histones and protamines, and, as a main update, a newly curated collection of 124 lncRNAs involved in epigenetic regulation. The amount of publications concerning the role of lncRNA in epigenetics is rapidly growing. Yet, the resource that compiles, integrates, organizes, and presents curated information on lncRNAs in epigenetics is missing. EpiFactors fills this gap and provides data on epigenetic regulators in an accessible and user-friendly form. For 820 of the genes in EpiFactors, we include expression estimates across multiple cell types assessed by CAGE-Seq in the FANTOM5 project. In addition, the updated EpiFactors contains information on 73 protein complexes involved in epigenetic regulation. Our resource is practical for a wide range of users, including biologists, bioinformaticians and molecular/systems biologists.

PDBrt: A free database of complexes with measured drug-target residence time

Background: Difficulties in translating the in vitro potency determined by cellular assays into in vivo efficacy in living organisms complicates the design and development of drugs. However, the residence time of a drug in its molecular target is becoming a key parameter in the design and optimization of new drugs, as recent studies show that residence time can reliably predict drug efficacy in vivo. Experimental approaches to binding kinetics and target ligand complex solutions are currently available, but known bioinformatics databases do not usually report information about the ligand residence time in its molecular target. Methods: To extend existing databases we developed the Protein Data Bank (PDB) residence time database (PDBrt) which reports drug residence time. The database is implemented as an open access web-based tool. The front end uses Bootstrap with Hypertext Markup Language (HTML), jQuery for the interface and 3Dmol.js to visualize the complexes. The server-side code uses Python web application framework, Django Rest Framework and backend database PostgreSQL. Results: The PDBrt database is a free, non-commercial repository for 3D protein-ligand complex data, including the measured ligand residence time inside the binding pocket of the specific biological macromolecules as deposited in The Protein Data Bank. The PDBrt database contains information about both the protein and the ligand separately, as well as the protein-ligand complex, binding kinetics, and time of the ligand residence inside the protein binding site. Availability: https://pdbrt.polsl.pl

An online database of RNA-small molecules complexes for rational drug design

The majority of approved drugs target proteins, which are encoded by a very small fraction of the human genome. When a pathology is associated with so-called undruggable proteins, an alternative strategy should be sought. In the last twenty years, non-coding RNA molecules have been shown to perform a variety of crucial biological functions, including regulating gene expression, protecting chromosomes from foreign nucleic acids, and guiding telomere synthesis. In this context, targeting RNA with small molecules is emerging as a promising therapeutic approach in pathologies such as cancer, viral infections, and neurodegenerative disorders.

PDBrt: A free database of complexes with measured drug-target residence time

Background: Difficulties in translating the in vitro potency determined by cellular assays into in vivo efficacy in living organisms complicates the design and development of drugs. However, the residence time of a drug in its molecular target is becoming a key parameter in the design and optimization of new drugs, as recent studies show that residence time can reliably predict drug efficacy in vivo. Experimental approaches to binding kinetics and target ligand complex solutions are currently available, but known bioinformatics databases do not usually report information about the ligand residence time in its molecular target. Methods: To extend existing databases we developed the Protein Data Bank (PDB) residence time database (PDBrt) which reports drug residence time. The database is implemented as an open access web-based tool. The front end uses Bootstrap with Hypertext Markup Language (HTML), jQuery for the interface and 3Dmol.js to visualize the complexes. The server-side code uses Python web application framework, Django Rest Framework and backend database PostgreSQL. Results: The PDBrt database is a free, non-commercial repository for 3D protein-ligand complex data, including the measured ligand residence time inside the binding pocket of the specific biological macromolecules as deposited in The Protein Data Bank. The PDBrt database contains information about both the protein and the ligand separately, as well as the protein-ligand complex, binding kinetics, and time of the ligand residence inside the protein binding site. Availability: https://pdbrt.polsl.pl

Complex Portal 2022: new curation frontiers.

The Complex Portal (www.ebi.ac.uk/complexportal) is a manually curated, encyclopaedic database of macromolecular complexes with known function from a range of model organisms. It summarizes complex composition, topology and function along with links to a large range of domain-specific resources (i.e. wwPDB, EMDB and Reactome). Since the last update in 2019, we have produced a first draft complexome for Escherichia coli, maintained and updated that of Saccharomyces cerevisiae, added over 40 coronavirus complexes and increased the human complexome to over 1100 complexes that include approximately 200 complexes that act as targets for viral proteins or are part of the immune system. The display of protein features in ComplexViewer has been improved and the participant table is now colour-coordinated with the nodes in ComplexViewer. Community collaboration has expanded, for example by contributing to an analysis of putative transcription cofactors and providing data accessible to semantic web tools through Wikidata which is now populated with manually curated Complex Portal content through a new bot. Our data license is now CC0 to encourage data reuse. Users are encouraged to get in touch, provide us with feedback and send curation requests through the ‘Support’ link.

Mapping of urban environmentally sensitive areas in Bratislava city

Environmentally sensitive areas within urban environment (U-ESA) play an essential role in maintaining urban ecological balance and ecological safety. The aims of our study were to analyse and evaluate the U-ESA spatial distribution in Bratislava city, in terms of the impact of sealed area, soil quality and urban green areas infrastructure as well as the occurrence of urban heat island in the summer months. These phenomena significantly reduce the ecological functions and ecosystem services of urban soils and can result in negative affect of the living standard and health condition of urban population. The methodology for assessing U-ESA is based on a multi-criteria process in which the following parameters have been identified and synthesized: pedo-urban complexes and their quality, urban heat island (UHI) areas and spatial distribution of urban vegetation types. Pedo-urban complexes (soil units including sealing areas, land use and soil degradation forms) were classified according to WRB. Georeferenced databases and maps became the basis for the identification of parameters involved within identification of U-ESA. Several partial products were compiled: vectorized land cover/land use categorized according to the Extended Nomenclature Urban Atlas 2012, database of pedo-urban complexes, modelled urban heat island map and map of urban vegetation types. Overlaying and synthesis of these partial results confirm thesis that sealed surfaces are one of the main causes of the increased incidence urban heat islands, but not entirely. The resulting U-ESA, designed areas in Bratislava, which are under increased risk in terms of quality of living standards. The key point of the research in the future is to find assessment of the soil quality in urbanized areas. We assume that the assessment should be based on ecosystem functions of pedo-urban complexes, i.e. anthropogenic soils. The identification of the U-ESA can be used for solving of housing comfort and quality of living standards in the frame of urban development and balanced spatial urban planning.

Hydrogen vs. Halogen Bonds in 1-Halo-Closo-Carboranes.

A theoretical study of the hydrogen bond (HB) and halogen bond (XB) complexes between 1-halo-closo-carboranes and hydrogen cyanide (NCH) as HB and XB probe has been carried out at the MP2 computational level. The energy results show that the HB complexes are more stable than the XBs for the same system, with the exception of the isoenergetic iodine derivatives. The analysis of the electron density with the quantum theory of atoms in molecules (QTAIM) shows the presence of a unique intermolecular bond critical point with the typical features of weak noncovalent interactions (small values of the electron density and positive Laplacian and total energy density). The natural energy decomposition analysis (NEDA) of the complexes shows that the HB and XB complexes are dominated by the charge-transfer and polarization terms, respectively. The work has been complemented with a search in the CSD database of analogous complexes and the comparison of the results, with those of the 1-halobenzene:NCH complexes showing smaller binding energies and larger intermolecular distances as compared to the 1-halo-closo-carboranes:NCH complexes.

Electrophilicity Indices and Halogen Bonds: Some New Alternatives to the Molecular Electrostatic Potential.

We assess the ability of various atomic and molecular electrophilicity descriptors to predict the strength of halogen bonds. To this aim, several physicochemical quantities rooted within the framework of conceptual density functional theory were derived using second and third order Taylor expansions of the electronic energy, and their correlation to binding energies were compared with those obtained for more usual electronic descriptors. This benchmark was performed for a large and representative database of noncovalent complexes involving fluorine, chlorine, and bromine atoms, and showed that some of these new quantities, in particular the atomic cubic electrophilicity index, exhibited more transferability and broadness of application than did more common descriptors such as the molecular electrostatic potential.

Disease Association and Druggability of WD40 Repeat Proteins.

WD40 repeat (WDR) domains are protein interaction scaffolds that represent one of the largest protein families in human, and a first WDR inhibitor-an allosteric antagonist of polycomb repressive complex 2-just entered the clinic. A systematic analysis of the CORUM database of protein complexes shows that WDR is the most represented domain in transcriptional regulation and one of the most prevalent in the ubiquitin proteasome system, two pathways of high relevance to drug discovery. Parsing the literature and the vulnerability of cancer cell lines to CRISPR knockout indicates that WDR proteins are targets of interest in oncology and other disease areas. A quantitative analysis of WDR structures reveals that druggable binding pockets can be found on multiple surfaces of these multifaceted protein interaction platforms. These data support the development of chemical probes to further interrogate WDR proteins as an emerging therapeutic target class.

FuzDB: database of fuzzy complexes, a tool to develop stochastic structure-function relationships for protein complexes and higher-order assemblies.

FuzDB (http://protdyn-database.org) compiles experimentally observed fuzzy protein complexes, where intrinsic disorder (ID) is maintained upon interacting with a partner (protein, nucleic acid or small molecule) and directly impacts biological function. Entries in the database have both (i) structural evidence demonstrating the structural multiplicity or dynamic disorder of the ID region(s) in the partner bound form of the protein and (ii) in vitro or in vivo biological evidence that indicates the significance of the fuzzy region(s) in the formation, function or regulation of the assembly. Unlike the other intrinsically disordered or unfolded protein databases, FuzDB focuses on ID regions within a biological context, including higher-order assemblies and presents a detailed analysis of the structural and functional data. FuzDB also provides interpretation of experimental results to elucidate the molecular mechanisms by which fuzzy regions—classified on the basis of topology and mechanism—interfere with the structural ensembles and activity of protein assemblies. Regulatory sites generated by alternative splicing (AS) or post-translational modifications (PTMs) are also collected. By assembling all this information, FuzDB could be utilized to develop stochastic structure–function relationships for proteins and could contribute to the emergence of a new paradigm.

Decomposing the space of protein quaternary structures with the interface fragment pair library.

BackgroundThe physical interactions between proteins constitute the basis of protein quaternary structures. They dominate many biological processes in living cells. Deciphering the structural features of interacting proteins is essential to understand their cellular functions. Similar to the space of protein tertiary structures in which discrete patterns are clearly observed on fold or sub-fold motif levels, it has been found that the space of protein quaternary structures is highly degenerate due to the packing of compact secondary structure elements at interfaces. Therefore, it is necessary to further decompose the protein quaternary structural space into a more local representation.ResultsHere we constructed an interface fragment pair library from the current structure database of protein complexes. After structural-based clustering, we found that more than 90% of these interface fragment pairs can be represented by a limited number of highly abundant motifs. These motifs were further used to guide complex assembly. A large-scale benchmark test shows that the native-like binding is highly likely in the structural ensemble of modeled protein complexes that were built through the library.ConclusionsOur study therefore presents supportive evidences that the space of protein quaternary structures can be represented by the combination of a small set of secondary-structure-based packing at binding interfaces. Finally, after future improvements such as adding sequence profiles, we expect this new library will be useful to predict structures of unknown protein-protein interactions.Electronic supplementary materialThe online version of this article (doi:10.1186/s12859-014-0437-4) contains supplementary material, which is available to authorized users.

Mining the human complexome database identifies RBM14 as an XPO1-associated protein involved in HIV-1 Rev function.

By recruiting the host protein XPO1 (CRM1), the HIV-1 Rev protein mediates the nuclear export of incompletely spliced viral transcripts. We mined data from the recently described human nuclear complexome to identify a host protein, RBM14, which associates with XPO1 and Rev and is involved in Rev function. Using a Rev-dependent p24 reporter plasmid, we found that RBM14 depletion decreased Rev activity and Rev-mediated enhancement of the cytoplasmic levels of unspliced viral transcripts. RBM14 depletion also reduced p24 expression during viral infection, indicating that RBM14 is limiting for Rev function. RBM14 has previously been shown to localize to nuclear paraspeckles, a structure implicated in retaining unspliced HIV-1 transcripts for either Rev-mediated nuclear export or degradation. We found that depletion of NEAT1 RNA, a long noncoding RNA required for paraspeckle integrity, abolished the ability of overexpressed RBM14 to enhance Rev function, indicating the dependence of RBM14 function on paraspeckle integrity. Our study extends the known host cell interactome of Rev and XPO1 and further substantiates a critical role for paraspeckles in the mechanism of action of Rev. Our study also validates the nuclear complexome as a database from which viral cofactors can be mined. This study mined a database of nuclear protein complexes to identify a cellular protein named RBM14 that is associated with XPO1 (CRM1), a nuclear protein that binds to the HIV-1 Rev protein and mediates nuclear export of incompletely spliced viral RNAs. Functional assays demonstrated that RBM14, a protein found in paraspeckle structures in the nucleus, is involved in HIV-1 Rev function. This study validates the nuclear complexome database as a reference that can be mined to identify viral cofactors.

EpiFactors: a comprehensive database of human epigenetic factors and complexes.

Epigenetics refers to stable and long-term alterations of cellular traits that are not caused by changes in the DNA sequence per se. Rather, covalent modifications of DNA and histones affect gene expression and genome stability via proteins that recognize and act upon such modifications. Many enzymes that catalyse epigenetic modifications or are critical for enzymatic complexes have been discovered, and this is encouraging investigators to study the role of these proteins in diverse normal and pathological processes. Rapidly growing knowledge in the area has resulted in the need for a resource that compiles, organizes and presents curated information to the researchers in an easily accessible and user-friendly form. Here we present EpiFactors, a manually curated database providing information about epigenetic regulators, their complexes, targets and products. EpiFactors contains information on 815 proteins, including 95 histones and protamines. For 789 of these genes, we include expressions values across several samples, in particular a collection of 458 human primary cell samples (for approximately 200 cell types, in many cases from three individual donors), covering most mammalian cell steady states, 255 different cancer cell lines (representing approximately 150 cancer subtypes) and 134 human postmortem tissues. Expression values were obtained by the FANTOM5 consortium using Cap Analysis of Gene Expression technique. EpiFactors also contains information on 69 protein complexes that are involved in epigenetic regulation. The resource is practical for a wide range of users, including biologists, pharmacologists and clinicians.Database URL: http://epifactors.autosome.ru

Structural Characterization of Heavy Metal Toxicity in a Human DNA Repair Glycosylase

The DNA base excision repair pathway consists of several enzymes, some of which require metal cations for catalysis. Human Uracil DNA Glycosylase (hUNG), a DNA glycosylase responsible for the initial detection and removal of carcinogenic lesions from DNA, is a non-metal requiring enzyme. Using biochemical assays we showed that cadmium II (Cd), a known human carcinogen, inhibits hUNG activity in the micromolar range. To provide mechanistic insights for metal enzyme interactions, we employed computational approaches based on MD and QM calculations. Initially, our 1 μs explicit solvent Molecular Dynamics simulations using the AMBER force field showed Cd entering the hUNG pocket, interacting with the catalytic D64 residue. Subsequent simulation at the PM3 level showed that Cd additionally interacts with H67 and the peptide oxygen of P65 in the presence of a chloride ion. This position effectively replaces the catalytic water essential for hUNG activity. Further quantum mechanical refinement using M06L/QZVP ONIOM of Gaussian 09 on structures obtained from the PM3 simulations produced two distinct geometries of Cd in coordination 5. Both hUNG-Cd complexes are in agreement with metal sites found in a recent database of protein-metal complexes (MetalPDB). This work for the first time demonstrates a possible binding interaction between hUNG and toxic metal. In concert with our biochemical data we propose that metal inhibition of hUNG is due to replacement of the catalytic water, where a stable metal complex forms and prevents catalysis. The inhibition of hUNG by Cd will enhance the mutagenic and carcinogenic potentials of a variety of parental genotoxic compounds.

Database of protein complexes with multivalent binding ability: Bival‐bind

Phenomena of multivalent binding of ligands with receptors are ubiquitous in biology and of growing interest in material sciences. Multivalency can enhance binding affinity dramatically. To understand the mechanism of multivalent binding in more detail model systems of bi- and multivalent receptors are needed, but are difficult to find. Furthermore it is useful to know about multivalent receptors, which can serve as targets to design multivalent drugs. The present contribution tries to close this gap. The Bival-Bind database (http://agknapp.chemie.fu-berlin.de/bivalbind) provides a relatively complete list - 2073 protein complexes with less than 90% sequence identity - out of the protein database, which can serve as bi- or multivalent receptors. Steric clashes of molecular spacers - necessary to connect the monomeric ligand units - with the receptor surface can diminish binding affinity dramatically and, thus, abolish the expected enhancement of binding affinity due to the multivalency. The potential multivalent receptors in the Bival-Bind database are characterized with respect to the receptor surface topography. A height profile between the receptor binding pockets is provided, which is an important information to estimate the influence of unfavorable spacer receptor interaction.

Searching for Likeness in a Database of Macromolecular Complexes

A software tool and workflow based on distance geometry is presented that can be used to search for local similarity in substructures in a comprehensive database of experimentally derived macromolecular structure. The method does not rely on fold annotation, specific secondary structure assignments, or sequence homology and may be used to locate compound substructures of multiple segments spanning different macromolecules that share a queried backbone geometry. This generalized substructure searching capability is intended to allow users to play an active part in exploring the role specific substructures play in larger protein domains, quaternary assemblies of proteins, and macromolecular complexes of proteins and polynucleotides. The user may select any portion or portions of an existing structure or complex to serve as a template for searching, and other structures that share the same structural features are identified, retrieved and overlaid to emphasize substructural likeness. Matching structures may be compared using a variety of integrated tools including molecular graphics for structure visualization and matching substructure sequence logos. A number of examples are provided that illustrate how generalized substructure searching may be used to understand both the similarity, and individuality of specific macromolecular structures. Web-based access to our substructure searching services is freely available at https://drugsite.msi.umn.edu.

Sampling strategy for protein complex prediction using cluster size frequency

In this paper we propose a Markov chain Monte Carlo sampling method for predicting protein complexes from protein–protein interactions (PPIs). Many of the existing tools for this problem are designed more or less based on a density measure of a subgraph of the PPI network. This kind of measures is less effective for smaller complexes. On the other hand, it can be found that the number of complexes of a size in a database of protein complexes follows a power-law. Thus, most of the complexes are small-sized. For example, in CYC2008, a database of curated protein complexes of yeast, 42% of the complexes are heterodimeric, i.e., a complex consisting of two different proteins. In this work, we propose a protein complex prediction algorithm, called PPSampler (Proteins' Partition Sampler), which is designed based on the Metropolis–Hastings algorithm using a parameter representing a target value of the relative frequency of the number of predicted protein complexes of a particular size. In a performance comparison, PPSampler outperforms other existing algorithms. Furthermore, about half of the predicted clusters that are not matched with any known complexes in CYC2008 are statistically significant by Gene Ontology terms. Some of them can be expected to be true complexes.