KSHV / gamma-herpesvirus / capsid structure / capsid-associated tegument protein / the smallest capsid protein / SCP
Function / homology
Function and homology information
T=16 icosahedral viral capsid / viral capsid assembly / viral process / viral capsid / host cell nucleus / structural molecule activity / DNA binding Similarity search - Function
Gammaherpesvirus capsid / Gammaherpesvirus capsid protein / Herpesvirus capsid shell protein 1 / Herpesvirus capsid shell protein VP19C / Herpesvirus capsid protein 2 / Herpesvirus VP23 like capsid protein / Herpesvirus major capsid protein / Herpesvirus major capsid protein, upper domain superfamily / Herpes virus major capsid protein Similarity search - Domain/homology
Journal: Proc Natl Acad Sci U S A / Year: 2015 Title: CryoEM and mutagenesis reveal that the smallest capsid protein cements and stabilizes Kaposi's sarcoma-associated herpesvirus capsid. Authors: Xinghong Dai / Danyang Gong / Yuchen Xiao / Ting-Ting Wu / Ren Sun / Z Hong Zhou / Abstract: With just one eighth the size of the major capsid protein (MCP), the smallest capsid protein (SCP) of human tumor herpesviruses--Kaposi's sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus ...With just one eighth the size of the major capsid protein (MCP), the smallest capsid protein (SCP) of human tumor herpesviruses--Kaposi's sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus (EBV)--is vital to capsid assembly, yet its mechanism of action is unknown. Here, by cryoEM of KSHV at 6-Å resolution, we show that SCP forms a crown on each hexon and uses a kinked helix to cross-link neighboring MCP subunits. SCP-null mutation decreased viral titer by 1,000 times and impaired but did not fully abolish capsid assembly, indicating an important but nonessential role of SCP. By truncating the C-terminal half of SCP and performing cryoEM reconstruction, we demonstrate that SCP's N-terminal half is responsible for the observed structure and function whereas the C-terminal half is flexible and dispensable. Serial truncations further highlight the critical importance of the N-terminal 10 aa, and cryoEM reconstruction of the one with six residues truncated localizes the N terminus of SCP in the cryoEM density map and enables us to construct a pseudoatomic model of SCP. Fitting of this SCP model and a homology model for the MCP upper domain into the cryoEM map reveals that SCP binds MCP largely via hydrophobic interactions and the kinked helix of SCP bridges over neighboring MCPs to form noncovalent cross-links. These data support a mechanistic model that tumor herpesvirus SCP reinforces the capsid for genome packaging, thus acting as a cementing protein similar to those found in many bacteriophages.
History
Deposition
Aug 12, 2014
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Header (metadata) release
Aug 27, 2014
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Map release
Sep 3, 2014
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Update
Mar 14, 2018
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Current status
Mar 14, 2018
Processing site: RCSB / Status: Released
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Structure visualization
Movie
Surface view with section colored by density value
Category: CCD / Film or detector model: GATAN K2 (4k x 4k) / Number real images: 8000 / Average electron dose: 25 e/Å2 Details: Every image is the average of 26 frames recorded by the direct electron detector.
Electron beam
Acceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
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