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How does the bean-pod mottle virus (BPMV) capsid structure differ from that of HRV?
How does the bean-pod mottle virus (BPMV) capsid structure differ from that of HRV?
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The capsid structures of the bean-pod mottle virus (BPMV) and human rhinovirus (HRV) exhibit several key differences, reflecting their distinct viral architectures and structural characteristics. Here are the main differences:
- Subunit Composition:
- BPMV: The BPMV capsid is composed of only two types of subunits: a small subunit and a large subunit. The small subunit contains one β-barrel domain, while the large subunit contains two β-barrel domains that remain covalently attached.
- HRV: In contrast, HRV capsids are made up of three different types of subunits: VP1, VP2, and VP3. Each of these subunits has a distinct structure and contributes to the overall architecture of the capsid.
- Capsid Size:
- BPMV: The BPMV capsid has a diameter of approximately 320 Å, which is similar to that of HRV but is constructed differently due to its fewer subunit types.
- HRV: HRV also has a diameter of about 320 Å, but its structure is more complex due to the presence of three different capsid proteins.
- Assembly and Quasi-Symmetry:
- BPMV: The BPMV capsid assembles into a T = 3-like shell, where the small subunit is equivalent to VP1 in HRV, and the large subunit corresponds to VP2 and VP3. This assembly is characterized by a simpler arrangement of fewer subunit types.
- HRV: HRV exhibits a T = 3 quasi-symmetry, where the three different subunits (VP1, VP2, and VP3) are arranged in a more complex manner, contributing to the formation of a viral canyon that is important for receptor binding.
- Structural Features:
- BPMV: The BPMV capsid structure features a more straightforward assembly with its two subunits, which can lead to a more uniform surface topology.
- HRV: The HRV capsid has a distinct “viral canyon” that encircles the fivefold axes, which is a deep cleft that plays a critical role in binding to cellular receptors (such as ICAM-1). This feature is not present in BPMV.
- Protein Folding and Interactions:
- BPMV: The folding of the BPMV subunits into β-barrel domains allows for effective assembly, but the interactions are less complex due to the reduced number of subunit types.
- HRV: The VP1, VP2, and VP3 subunits in HRV exhibit more complex folding patterns and interactions, which contribute to the structural diversity and functional capabilities of the capsid.
- Functionality and Host Interaction:
- BPMV: The simpler structure of BPMV may influence its interactions with host cells and its overall functionality, particularly in plant hosts.
- HRV: The more complex structure of HRV, including the viral canyon, is specifically adapted for interactions with human cell receptors, facilitating its entry into host cells.
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