Molecular rearrangements involved in the capsid shell maturation of bacteriophage T7.
Maturation of dsDNA bacteriophages involves assembling the virus prohead from a limited set of structural components followed by rearrangements required for the stability that is necessary for infecting a host under challenging environmental conditions. Here, we determine the mature capsid structure of T7 at 1 nm resolution by cryo-electron microscopy and compare it with the prohead to reveal the molecular basis of T7 shell maturation. The mature capsid presents an expanded and thinner shell, with a drastic rearrangement of the major protein monomers that increases in their interacting surfaces, in turn resulting in a new bonding lattice. The rearrangements include tilting, in-plane rotation, and radial expansion of the subunits, as well as a relative bending of the A- and P-domains of each subunit. The unique features of this shell transformation, which does not employ the accessory proteins, inserted domains, or molecular interactions observed in other phages, suggest a simple capsid assembling strategy that may have appeared early in the evolution of these viruses.
Department of Macromolecular Structure, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, Darwin 3, Cantoblanco, 28049 Madrid, Spain.
Alina
A
Ionel
Javier A
JA
Velázquez-Muriel
Daniel
D
Luque
Ana
A
Cuervo
José R
JR
Castón
José M
JM
Valpuesta
Jaime
J
Martín-Benito
José L
JL
Carrascosa
D017123:Bacteriophage T7 / Q000378:metabolism / Q000502:physiology*; D002213:Capsid / Q000737:chemistry* / Q000378:metabolism*; D036022:Capsid Proteins / Q000737:chemistry / Q000378:metabolism; D020285:Cryoelectron Microscopy; D008958:Models, Molecular; D017434:Protein Structure, Tertiary
D036022:Capsid Proteins