Amino acids at the exposed C-terminus of the S coat protein of cowpea mosaic virus play different roles in particle formation and viral systemic movement.

Yulia Meshcheriakova,George P Lomonossoff

doi:10.1099/jgv.0.001285

Yulia Meshcheriakova, George P Lomonossoff

Open Access

https://doi.org/10.1099/jgv.0.001285

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Abstract

The icosahedral capsid of cowpea mosaic virus is formed by 60 copies of the large (L) and small (S) coat protein subunits. The 24-amino-acid C-terminal peptide of the S coat protein can undergo proteolytic cleavage without affecting particle stability or infectivity. Mutagenic studies have shown that this sequence is involved in particle assembly, virus movement, RNA encapsidation and suppression of gene silencing. However, it is unclear how these processes are related, and which part(s) of the sequence are involved in each process. Here, we have analysed the effect of mutations in the C-terminal region of the S protein on the assembly of empty virus-like particles and on the systemic movement of infectious virus. The results confirmed the importance of positively charged amino acids adjacent to the cleavage site for particle assembly and revealed that the C-terminal 11 amino acids are important for efficient systemic movement of the virus.

Highlights

The icosahedral capsid of cowpea mosaic virus is formed by 60 copies of the large (L) and small (S) coat protein subunits
The two genomic RNA molecules (RNA-1 and RNA-2) are separately encapsidated within icosahedral particles, consisting of 60 copies each of the large (L) and small (S) coat proteins, which are produced by proteolytic processing of a precursor, VP60 [1, 2]; the structure of the virions is known to atomic resolution [3]
System for the production of Cowpea mosaic virus (CPMV) empty virus-like particles through transient expression of coat protein precursor, VP60, and the viral 24K protease necessary for its processing [2] has enabled the process of capsid formation to be studied in the absence of infection

Summary

Introduction

The icosahedral capsid of cowpea mosaic virus is formed by 60 copies of the large (L) and small (S) coat protein subunits. The effect of the mutations on the assembly of empty virus-like particles (eVLPs) after transient expression and on the ability of infectious virus to move systemically is shown.

Results

Conclusion