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Viral Structure

Viral Structure

Viruses are extraordinarily diverse in shape and size, but they all have several structural features in common. All viruses have a core that contains a DNA- or RNA-based genome. The core is surrounded by a protective coat of proteins called the capsid. The capsid is composed of subunits called capsomeres. The capsid and genome-containing core are together known as the nucleocapsid.

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What are Viruses?

Retrovirus Life Cycles

Retrovirus Life Cycles

Retroviruses have a single-stranded RNA genome that undergoes a special form of replication. Once the retrovirus has entered the host cell, an enzyme called reverse transcriptase synthesizes double-stranded DNA from the retroviral RNA genome. This DNA copy of the genome is then integrated into the host’s genome inside the nucleus via an enzyme called integrase. Consequently, the retroviral genome is transcribed into RNA whenever the host’s genome is transcribed, allowing the...

Intracellular Movement of Viruses and Bacteria

Intracellular Movement of Viruses and Bacteria

Intracellular bacteria and viruses often comprise a group of highly infectious pathogens that can cause several diseases. Bacterial pathogens include those belonging to the genus Rickettsia responsible for conditions such as rocky mountain spotted fever and the Mediterranean spotted fever; Chlamydia, a genus responsible for a sexually transmitted disease; Coxiella burnetii, an agent responsible for Q fever. Viral pathogens include vaccinia—a poxvirus, and herpes simplex virus—a...

Retroviruses

Retroviruses

Retroviruses and retrotransposons both insert copies of their genetic elements into the genome of the host cell. Thus, the viral genes are passed on when the host genome is replicated or translated. A typical retroviral DNA sequence contains 3-4 genes that encode the different proteins required for its structural assembly and function as a molecular parasite. This DNA is transcribed into a single mRNA, which is very similar in structure to conventional mRNAs, i.e., it is capped at the 5’...

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Related Experiment Video

Updated: May 7, 2025

Generation and Assembly of Virus-Specific Nucleocapsids of the Respiratory Syncytial Virus

Generation and Assembly of Virus-Specific Nucleocapsids of the Respiratory Syncytial Virus

Published on: July 27, 2021

The Basic Architecture of Viruses.

José R Castón¹

¹Department of Macromolecular Structure, Centro Nacional de Biotecnología (CNB-CSIC), Madrid, Spain. jrcaston@cnb.csic.es.

Sub-Cellular Biochemistry

|December 31, 2024

Summary

Viruses utilize symmetry and protein flexibility to build capsids efficiently. Studying viral structures reveals fundamental principles applicable to other biological macromolecules.

Keywords:

Capsid Conformational polymorphism Helical symmetry Icosahedral symmetry Metastable capsid Molecular switch Nucleocapsid Prolate capsid Quasi-equivalence Triangulation number

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Related Experiment Videos

Last Updated: May 7, 2025

Generation and Assembly of Virus-Specific Nucleocapsids of the Respiratory Syncytial Virus

Generation and Assembly of Virus-Specific Nucleocapsids of the Respiratory Syncytial Virus

Published on: July 27, 2021

Simple and Robust in vivo and in vitro Approach for Studying Virus Assembly

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Published on: March 1, 2012

Combining Analysis of DNA in a Crude Virion Extraction with the Analysis of RNA from Infected Leaves to Discover New Virus Genomes

Combining Analysis of DNA in a Crude Virion Extraction with the Analysis of RNA from Infected Leaves to Discover New Virus Genomes

Published on: July 27, 2018

Area of Science:

Structural biology
Virology
Biophysics

Background:

Viruses are efficient macromolecular assemblies economizing genomic resources.
Viral structure relies on symmetry (icosahedral, helical) and protein flexibility.
Diverse virus structures originate from limited basic schemes with added complexity.

Purpose of the Study:

To explore the principles of viral capsid assembly.
To understand the relationship between viral structure and function.
To highlight the broader implications of viral structural studies.

Main Methods:

Analysis of viral protein structures.
Examination of symmetry principles in viral assembly.
Investigation of protein conformational flexibility.

Main Results:

Viruses employ limited structural subunits extensively using symmetry.
Conformational flexibility of viral proteins leads to dynamic capsids.
Viral structures demonstrate a limited set of fundamental assembly schemes.

Conclusions:

Viral structure-function relationships are key to understanding viral life cycles.
Principles of viral assembly offer insights into other macromolecular complexes.
Structural virology provides a foundation for understanding fundamental biological processes.