Evolution in action: N and C termini of subunits in related T = 4 viruses exchange roles as molecular switches.
The T = 4 tetravirus and T = 3 nodavirus capsid proteins undergo closely similar autoproteolysis to produce the N-terminal beta and C-terminal, lipophilic gamma polypeptides. The gamma peptides and the N termini of beta also act as molecular switches that determine their quasi equivalent capsid structures. The crystal structure of Providence virus (PrV), only the second of a tetravirus (the first was NomegaV), reveals conserved folds and cleavage sites, but the protein termini have completely different structures and the opposite functions of those in NomegaV. N termini of beta form the molecular switch in PrV, whereas gamma peptides play this role in NomegaV. PrV gamma peptides instead interact with packaged RNA at the particle two-folds by using a repeating sequence pattern found in only four other RNA- or membrane-binding proteins. The disposition of peptide termini in PrV is closely related to those in nodaviruses, suggesting that PrV may be closer to the primordial T = 4 particle than NomegaV.
Speir
Jeffrey A
JA
Department of Molecular Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
Taylor
Derek J
DJ
Natarajan
Padmaja
P
Pringle
Fiona M
FM
Ball
L Andrew
LA
Johnson
John E
JE
D001483:Base Sequence; D005075:Biological Evolution; D002213:Capsid / Q000737:chemistry / Q000378:metabolism; D036022:Capsid Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012328:RNA Viruses / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014780:Viruses / Q000235:genetics*
D036022:Capsid Proteins