Padmaja Natarajan

VIPERdb2: an enhanced and web API enabled relational database for structural virology.

VIPERdb (http://viperdb.scripps.edu) is a relational database and a web portal for icosahedral virus capsid structures. Our aim is to provide a comprehensive resource specific to the needs of the virology community, with an emphasis on the description and comparison of derived data from structural and computational analyses of the virus capsids. In the current release, VIPERdb2, we implemented a useful and novel method to represent capsid protein residues in the icosahedral asymmetric unit (IAU) using azimuthal polar orthographic projections, otherwise known as Φ–Ψ (Phi–Psi) diagrams. In conjunction with a new Application Programming Interface (API), these diagrams can be used as a dynamic interface to the database to map residues (categorized as surface, interface and core residues) and identify family wide conserved residues including hotspots at the interfaces. Additionally, we enhanced the interactivity with the database by interfacing with web-based tools. In particular, the applications Jmol and STRAP were implemented to visualize and interact with the virus molecular structures and provide sequence–structure alignment capabilities. Together with extended curation practices that maintain data uniformity, a relational database implementation based on a schema for macromolecular structures and the APIs provided will greatly enhance the ability to do structural bioinformatics analysis of virus capsids.

Virus Particle Explorer (VIPER), a Website for Virus Capsid Structures and Their Computational Analyses

The number of icosahedral-capsid structures determined at a near-atomic level of resolution is growing rapidly as advances in synchrotron radiation sources, fast-readout detectors, and computer hardware and software are made. Hence, there is an increasing need to organize these mega-assemblies into a uniform and easy-to-use database. The coordinates of the icosahedral-capsid structures deposited in the Protein Data Bank (PDB) (2) follow a variety of conventions in which the icosahedral symmetry axes are oriented differently in the orthogonal coordinate system. While trying to analyze the various capsid structures en masse, we became aware of the need for a database in which all capsid structures (coordinates) are stored in a standard icosahedral orientation. Such a structural database of viral capsids would indeed facilitate the development of tools for high-throughput analyses of the virus structures. We report here the creation of a web-base (website and database) of virus structures, the Virus Particle Explorer (VIPER), which can be accessed through the World Wide Web (WWW) at the uniform resource locator (URL) http://mmtsb.scripps.edu /viper/. The organization of the VIPER database is shown in Fig. ​Fig.1.1. FIG. 1 Flow chart showing the organization of the contents of the VIPER site. The VIPER database contains the structures of viral capsids determined at a nearly atomic-level resolution. Coordinates of the capsid structures are stored in the z(2)-3-5-x(2) convention. ...

VIPERdb: a relational database for structural virology

VIPERdb () is a database for icosahedral virus capsid structures. Our aim is to provide a comprehensive resource specific to the needs of the structural virology community, with an emphasis on the description and comparison of derived data from structural and energetic analyses of capsids. A relational database implementation based on a schema for macromolecular structure makes the data highly accessible to the user, allowing detailed queries at the atomic level. Together with curation practices that maintain data uniformity, this will facilitate structural bioinformatics studies of virus capsids. User friendly search, visualization and educational tools on the website allow both structural and derived data to be examined easily and extensively. Links to relevant literature, sequence and taxonomy databases are provided for each entry.

Exploring icosahedral virus structures with VIPER

Virus structures are megadalton nucleoprotein complexes with an exceptional variety of protein–protein and protein–nucleic-acid interactions. Three-dimensional crystal structures of over 70 virus capsids, from more than 20 families and 30 different genera of viruses, have been solved to near-atomic resolution. The enormous amount of information contained in these structures is difficult to access, even for scientists trained in structural biology. Virus Particle Explorer (VIPER) is a web-based catalogue of structural information that describes the icosahedral virus particles. In addition to high-resolution crystal structures, VIPER has expanded to include virus structures obtained by cryo-electron microscopy (EM) techniques. The VIPER database is a powerful resource for virologists, microbiologists, virus crystallographers and EM researchers. This review describes how to use VIPER, using several examples to show the power of this resource for research and educational purposes.

Correlation of chemical reactivity of Nudaurelia capensis ω virus with a pH-induced conformational change

Nudaurelia capensis omega virus, which undergoes one of the largest known structural changes of icosahedral viruses in response to its environment, exhibits chemical reactivity which depends on its conformational state.

Evolution in Action: N and C Termini of Subunits in Related T = 4 Viruses Exchange Roles as Molecular Switches

The T = 4 tetravirus and T = 3 nodavirus capsid proteins undergo closely similar autoproteolysis to produce the N-terminal beta and C-terminal, lipophilic gamma polypeptides. The gamma peptides and the N termini of beta also act as molecular switches that determine their quasi equivalent capsid structures. The crystal structure of Providence virus (PrV), only the second of a tetravirus (the first was NomegaV), reveals conserved folds and cleavage sites, but the protein termini have completely different structures and the opposite functions of those in NomegaV. N termini of beta form the molecular switch in PrV, whereas gamma peptides play this role in NomegaV. PrV gamma peptides instead interact with packaged RNA at the particle two-folds by using a repeating sequence pattern found in only four other RNA- or membrane-binding proteins. The disposition of peptide termini in PrV is closely related to those in nodaviruses, suggesting that PrV may be closer to the primordial T = 4 particle than NomegaV.

Resolution of space-group ambiguity and structure determination of nodamura virus to 3.3 A resolution from pseudo-R32 (monoclinic) crystals.

Monoclinic crystals of nodamura virus (NOV) have two virus molecules per asymmetric unit. Packing analysis reveals a pseudo-rhombohedral (pseudo-C2 monoclinic) arrangement of particles in the actual P2(1) space group (a = 562.1, b = 354.1, c = 612.8 A, beta = 110.9 degrees ). The R32 symmetry is broken rotationally and translationally. The pseudo-symmetry of the unit cell results in three possible monoclinic origins and also restrains the four particles in the unit cell to similar orientations. NOV particles deviate by less than 3 degrees from the ideal orientations, causing overlap of peaks in the rotation function and the generation of peaks that were not interpretable as particle symmetry elements. The space-group ambiguity was resolved by analysing the relationship between the particle orientations determined by high-resolution rotation functions and the attenuation of peak heights in native Patterson maps. Particles were centered less than 1 A from the R32 special positions. Three different approaches were required to identify the correct particle center. Following the solutions of the rotation and translation problems, phases were computed using the coordinates of flock house virus (FHV), another member of this virus family. The phases were improved by real-space molecular averaging with a 120-fold non-crystallographic symmetry and by solvent flattening with a spherical mask. The final model for the NOV structure was built using the 3.3 A averaged map. While the overall subunit structure was very similar to that of other nodaviruses, FHV and black beetle virus, NOV showed distinct structural features near particle threefold and quasi-threefold axes and at the protein-RNA interfaces that are consistent with phenotype differences among the related viruses.