role of inter-subunit ionic interactions in the assembly of Physalis mottle tymovirus

• Published in: Archives of virology Vol. 151; no. 10; pp. 1917 - 1931
• Main Authors: Umashankar, M, Murthy, M. R. N, Singh, S. A, Appu Rao, A. G, Savithri, H. S
• Format: Journal Article
• Language: English
• Published: Wien Vienna : Springer-Verlag 01.10.2006; New York, NY Springer; Springer Nature B.V
• Subjects: Biological and medical sciences; Capsid Proteins - chemistry; Capsid Proteins - genetics; Capsid Proteins - metabolism; Capsid Proteins - physiology; DNA polymerase; E coli; Fundamental and applied biological sciences. Psychology; Genomes; Ions - metabolism; Microbiology; Miscellaneous; Models, Molecular; Mutagenesis; Mutagenesis, Site-Directed; Physalis; Physalis - virology; Physalis mottle tymovirus; Protein Folding; Protein Subunits - chemistry; Protein Subunits - metabolism; Protein Subunits - physiology; Proteins; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Tymovirus; Tymovirus - chemistry; Tymovirus - physiology; Virology; Virus Assembly; Viruses; Virus; Tymovirus; Plant pathogen; Physalis; Dicotyledones; Angiospermae; Herbaceous plant; Spermatophyta; Solanaceae; Subunit; Tymoviridae
• ISSN: 0304-8608; 1432-8798
• DOI: 10.1007/s00705-006-0783-2

Physalis mottle tymovirus (PhMV) is a small spherical plant virus with its RNA genome encapsidated in a protein shell made of 180 identical coat protein (CP) subunits. The amino acid residues involved in two interfacial salt bridges, Asp-83/Arg-159 and Arg-68/Asp-150 and Lys-153, were targeted for mutagenesis with a view to delineate the role of interfacial ionic interactions in the subunit folding and assembly of the virus. R159A and D83A-R159A recombinant CP (rCP) mutants formed stable T = 3 capsids, indicating that the D83-R159 interfacial salt bridge is dispensable for the folding and assembly of PhMV. However, D150A and R68Q-D150A mutant rCPs were present in the insoluble fraction, suggesting that the R68-D150 interfacial salt bridge is crucial for subunit folding and assembly. Similarly, K153Q, D83A-K153Q, and H69A-K153Q mutant rCPs were present in the insoluble fraction. Interestingly, the R68Q-D150A, D83A-K153Q, and H69A-K153Q double mutant rCPs could be refolded into partially folded soluble heterogeneous aggregates of 14-16 S. The results further confirm our earlier observation that subunit folding and assembly are concerted events in PhMV.