L4 - Viral structure Flashcards
Many viruses exhibit icosahedral symmetry, characterised by 20 triangular faces and 12 vertices.
Many viruses exhibit icosahedral symmetry, characterised by 20 triangular faces and 12 vertices.
What are the key features of an icosahedron in virus structure?
An icosahedron has rotational symmetry axes of 2-, 3-, and 5-fold, which dictate its overall shape and assembly.
How does helical symmetry differ from icosahedral symmetry in viruses?
Helical symmetry involves the formation of a nucleocapsid with a spiral or rod-like structure, common among enveloped RNA viruses.
Why is understanding virus symmetry important for structural studies?
It aids in determining the assembly, stability, and potential targets for antiviral drugs.
What advantage does cryo-electron microscopy offer over traditional electron microscopy?
Cryo-EM preserves the native hydrated state of viruses and enables high-resolution 3D reconstructions.
How does X‑ray crystallography contribute to our understanding of virus structure?
It provides atomic resolution details of virus components, although it requires the virus or its parts to form crystals.
What role does cryo-electron tomography play in virus research?
It allows for visualisation of large, asymmetrical biological assemblies, including viruses in a near-native state.
How have AI approaches, such as AlphaFold, advanced virus structural studies?
They refine cryo-EM reconstructions, predict protein structures from sequences, and aid in mapping evolutionary relationships.
What was significant about the X‑ray structure determination of poliovirus?
It revealed the “β‐jelly roll” structure of capsid proteins and provided a framework for understanding viral assembly.
What is the benefit of combining X‑ray and cryo‑EM techniques in viral studies?
This combination allows for the detailed characterisation of both static high-resolution structures and dynamic viral rearrangements.
How can structural knowledge of viruses be applied in medical research?
It underpins rational drug design, structure-based vaccine development, and even strategies for rational attenuation of viruses.
What are the key areas covered in the study of virus structure?
The study includes virus symmetry, methods to determine structures (e.g. cryo-EM, X‑ray crystallography), atomic-resolution structures, and applications such as antiviral drug design and vaccine development.
How has structural knowledge advanced our understanding of virus entry and evolution?
Detailed structures reveal dynamic rearrangements during entry, inform fusion mechanisms, and help trace evolutionary relationships among viruses.
Why is it important to study virus structure at atomic resolution?
Atomic-level details allow for precise identification of functional domains, interactions with host receptors, and targeted design of antiviral compounds.
In what ways is virus structure utilised in modern medicine?
It is applied to structure-based vaccine design, rational drug design, and even the attenuation of viruses for safe vaccine development.
What is icosahedral symmetry and why is it common in viruses?
Icosahedral symmetry refers to a spherical arrangement with 20 triangular faces and 12 vertices, optimising structural stability and efficient assembly with limited genetic material.
How many faces and vertices does an icosahedron have?
An icosahedron has 20 faces and 12 vertices.
What are the rotational symmetry axes in an icosahedron?
The axes are 2-fold, 3-fold, and 5-fold, which determine the uniform distribution of capsid proteins.
Why is icosahedral symmetry advantageous for virus assembly?
It allows viruses to form a closed shell using multiple copies of a few protein types, minimising genetic complexity while maximising structural strength.
What characterises helical virus structures?
Helical viruses have a nucleocapsid that forms a spiral or rod-like structure, often seen in enveloped RNA viruses.
How does the assembly of helical viruses differ from icosahedral viruses?
Helical viruses assemble by polymerising capsid proteins along the viral RNA, forming a flexible and elongated structure.
In what types of viruses are helical structures typically observed?
They are common in many enveloped animal RNA viruses, such as those in the Paramyxoviridae family.
Why might a helical structure be beneficial for certain viruses?
Helical structures can accommodate long strands of RNA and may allow for greater flexibility in the virus particle.
What are the main techniques used to study virus structure?
Key methods include electron microscopy (EM), cryo-electron microscopy (cryo-EM), and X‑ray crystallography.
How does cryo-EM differ from traditional EM?
Cryo-EM involves rapid freezing of samples in their native hydrated state, preserving natural structure and enabling high-resolution 3D reconstructions.
What is a limitation of X‑ray crystallography in virus studies?
It requires the formation of crystals, which may be challenging for large or flexible virus particles.
How has the resolution of cryo-EM advanced in recent years?
Cryo-EM resolution has improved to below 2 Å, allowing for near-atomic detail in virus structures.
What was significant about the X‑ray structure of poliovirus?
The structure revealed a “β‑jelly roll” motif in the capsid proteins, enhancing understanding of virus assembly and stability.
How has the structure of influenza haemagglutinin (HA) contributed to our knowledge of virus entry?
The X‑ray structure of HA delineated receptor-binding and fusion domains, clarifying how the virus binds to host cells and initiates fusion
What does the combination of X‑ray and cryo‑EM studies provide in viral structural analysis?
It integrates high-resolution static details with dynamic, near-native state visualisation, leading to a comprehensive understanding of viral architecture.
Why are structural studies of viruses critical for developing antiviral therapies?
Detailed structures enable the design of molecules that specifically target viral components, disrupting key processes such as fusion and replication.
How are X‑ray and cryo‑EM techniques combined to study flaviviruses?
X‑ray crystallography provides atomic details of individual proteins, while cryo‑EM visualises the intact virus particle and its overall architecture.
What is the advantage of combining these two methods for flaviviruses?
The integration allows researchers to map high-resolution protein structures onto the overall virion, revealing how structural rearrangements occur during maturation and fusion.
How does the flavivirus E protein change upon exposure to acidic pH?
It undergoes a conformational rearrangement from a dimeric to a trimeric postfusion state, facilitating membrane fusion.
What are some applications of the structural knowledge obtained from flavivirus studies?
These include rational vaccine design, antiviral drug development, and improved understanding of virus-host interactions and immune evasion.
How does structural information contribute to rational antiviral drug design?
It allows for the identification of binding sites and active domains on viral proteins, enabling the design of inhibitors that disrupt critical viral functions.
What role does virus structure play in vaccine development?
Structural insights enable the design of immunogens that mimic the native virus, eliciting a robust immune response.
How can structural studies inform the rational attenuation of viruses for vaccine use?
By understanding the structural determinants of virulence, specific mutations can be introduced to reduce pathogenicity without compromising immunogenicity.
In what way does structural information help in understanding virus evolution?
Comparative analysis of virus structures can reveal conserved elements and evolutionary relationships, informing both epidemiology and the development of broad-spectrum antivirals.
What is recombineering, and how is it used in virus research?
Recombineering is a genetic engineering technique that allows for targeted modifications of viral genomes, aiding in functional studies and vaccine development.
How do viral envelopes contribute to host cell entry?
Viral envelopes help the virus fuse with host cell membranes, facilitating entry and infection.
What is the role of spike proteins in enveloped viruses?
Spike proteins mediate attachment and entry into host cells by binding to specific receptors.
How does the presence of an envelope impact viral stability?
Enveloped viruses are often less stable in the environment but can evade the immune system more effectively.
What factors determine whether a virus has an envelope?
A virus acquires an envelope if it buds from the host cell membrane rather than lysing the cell.
Why do some viruses lack an envelope, and how does this affect their transmission?
Non-enveloped viruses are generally more resistant to environmental conditions and tend to spread via the fecal-oral route.
What distinguishes a capsid from an envelope in viral structure?
The capsid is a protein shell that encloses the viral genome, whereas an envelope is derived from the host membrane and surrounds the capsid.
How does icosahedral symmetry contribute to efficient genome packaging?
Icosahedral symmetry allows viruses to form stable, closed structures using minimal genetic material.
What is the significance of helical symmetry in viral architecture?
Helical symmetry enables flexible genome encapsidation and is commonly seen in RNA viruses.
What are the key differences between icosahedral and helical virus structures?
Icosahedral viruses form compact, spherical particles, while helical viruses form elongated, rod-like structures.
How does electron microscopy contribute to viral morphology studies?
Electron microscopy provides a general view of viral morphology, including size and shape.
What are the limitations of traditional electron microscopy in studying virus structure?
Traditional electron microscopy has limited resolution and may not reveal fine structural details.
Why is cryo-electron microscopy particularly useful for studying viruses?
Cryo-EM allows for high-resolution imaging of viruses in a near-native hydrated state.
How does rapid freezing in cryo-EM preserve viral structure?
Rapid freezing prevents ice crystal formation, preserving the virus in a close-to-natural conformation.
What advantage does cryo-EM have over X-ray crystallography in viral studies?
Cryo-EM does not require crystallization and can resolve flexible or complex viral structures.
Why is crystallization a challenge in X-ray crystallography for viruses?
Crystallization can be difficult for large or dynamic viruses, limiting the applicability of X-ray crystallography.
What are some key viral components that have been studied using X-ray crystallography?
Hemagglutinin and neuraminidase from influenza viruses have been studied using X-ray crystallography.
How does structural knowledge of viruses aid in vaccine development?
Understanding virus structure helps in designing vaccines that target key viral proteins.
Why is the stabilization of viral proteins important for vaccine efficacy?
Stabilizing viral proteins ensures they maintain the correct conformation for an effective immune response.
How has structural virology contributed to the development of SARS-CoV-2 vaccines?
Structural virology enabled the design of stabilized spike protein variants used in COVID-19 vaccines.
What is an example of a drug that was designed based on viral structural knowledge?
Neuraminidase inhibitors, such as oseltamivir (Tamiflu), were developed based on viral structural insights.
How does structural knowledge help in designing antiviral drugs?
Identifying viral entry mechanisms and active sites enables the creation of targeted antiviral drugs.
What role does viral structure play in understanding zoonotic transmission?
Structural comparisons help predict how viruses evolve and jump between species.
How does AlphaFold contribute to structural virology?
AlphaFold predicts viral protein structures from sequence data, accelerating structural analysis.
What are the benefits of using AI-based tools in viral structure prediction?
AI tools streamline the identification of viral epitopes and drug targets by predicting structural conformations.
How has AI advanced the study of flaviviruses?
AI-based approaches have revealed new structural variants in flaviviruses, improving vaccine and drug strategies.
What structural features of flaviviruses have been identified using AI tools?
Structural studies have mapped flavivirus surface proteins, aiding in understanding their immune evasion strategies.
How do structural studies contribute to understanding virus-host interactions?
Viral evolution studies inform strategies to develop broad-spectrum antivirals and future vaccines.
Why is studying viral evolution important for vaccine and drug development?
