A highly basic KGKKGK sequence in the RNA-binding domain of the Cucumber necrosis virus coat protein is associated with encapsidation of full-length CNV RNA during infection.
The Cucumber necrosis virus particle is a T=3 icosahedron consisting of 180 identical coat protein (CP) subunits. The N-terminal 58 aa residue segment of the CP R domain is believed to bind viral RNA within virions and during assembly. We report results of in vivo experiments that examine the role of the R domain in assembly. Deletion analyses identified 3 conserved 5-10 aa regions as playing critical roles. A highly basic KGKKGK sequence was found to be both necessary and sufficient for encapsidation of the full-length genome and polymorphic virions were produced in mutants lacking the KGKKGK sequence. The amount of full-length RNA present in virions was substantially reduced in R domain mutants where 2 of the 4 lysine residues were substituted with alanine, whereas substitution of 4 lysines by arginine had only a modest effect. The potential role of the R domain in formation of a scaffold for particle assembly is discussed.
Reade
Ron
R
Pacific Agri-Food Research Centre, Summerland, British Columbia, Canada V0H 1Z0.
Kakani
Kishore
K
Rochon
D'Ann
D
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D001665:Binding Sites; D036022:Capsid Proteins / Q000235:genetics / Q000378:metabolism*; D017124:Conserved Sequence; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D012367:RNA, Viral / Q000378:metabolism*; D017384:Sequence Deletion; D014026:Nicotiana / Q000821:virology; D017864:Tombusvirus / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D014771:Virion / Q000648:ultrastructure; D019065:Virus Assembly
D036022:Capsid Proteins; D012367:RNA, Viral