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Publication Abstract from PubMed

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.

Evolution in action: N and C termini of subunits in related T = 4 viruses exchange roles as molecular switches.,Speir JA, Taylor DJ, Natarajan P, Pringle FM, Ball LA, Johnson JE Structure. 2010 Jun 9;18(6):700-9. PMID:20541507^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.