Architectural Details of Virus Particles by Electron Nanobioimaging (MINIREVIEW)

Nagwa Mohamed Amin Aref*

Department of Botany &Microbiology/College of Science/King Saud University/ Riyadh/KSA

E-mail: narif@ksu.edu.sa & nagwa_aref@hotmail.com

            Virus particles are nanometer-scale biological systems that are essential to our daily life and human health. From an engineering point of view, viruses are delicate nano-machines with functionalities greatly exceeding any man-made nano-devices .A better understanding of the structures (or “designs”) of these biological nanomachines would provide important guidance for engineering more efficient nano-devices and such approach has become increasingly recognized for nano scientists worldwide. Unique studies had developed the software package, IMIRS (Image Management and Icosahedral Reconstruction System), which is integrated with a distributed relational database for managing complex datasets. The modular programs in IMIRS are parallelized to run on high-performance multiprocessor computer servers. The integration of data management with processing in IMIRS automates the tedious tasks of data management, enables data coherence, and facilitates information sharing in a distributed environment. Structural studies on virus/host by cryo-electron microscopy (cryoEM) and cryo-electron tomography (cryoET) reveal structural and architectural details related to virus-host interactions. For understand the mechanisms governing macromolecular functions by pushing the resolution limit of cryoEM to near-atomic resolution and by describing large, pleomorphic, dynamic structures or conformations using the integrative approach of cryoEM single particle reconstruction. Structural studies have also shown that large-scale conformational changes transform phage precursors into infectious virions. A family of "diversity-generating retroelements" (DGRs) that function to diversify DNA sequences and the proteins they encode has recently been identified of bacteriophage at molecular to 7-Å resolutions using cryoET and cryoEM that has been determined respectively. DGRs are unique for its ability of rapidly switching its infection specificity by varying the gene using a novel “diversity-generating retroelement” which changes the binding affinity to the bacterial receptors. Most notably study also, has demonstrated recently that cryoEM structures can be determined to 3.8-Å resolution which reveals side chains of some amino acid residues, allowing us to construct a preliminary atomic model. In that map, β strands can be resolved and some bulky amino-acid side chains can be readily identified. From this cryoEM derived density map, an atomic model of 3.88A° structure of Cytoplasmic polyhedrosis virus (CPV) have been built and identified conformational switches that are implicated in regulating RNA sliding. Pushing the envelope of cryoEM imaging to atomic resolution will allow us to understand the molecular interactions essential to virus assembly in atomic detail.

Keywords: cryoEM , cryoET, IMIRS, Nanobiotechnology and virus particles.