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.
Ionel
Alina
A
Department of Macromolecular Structure, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, Darwin 3, Cantoblanco, 28049 Madrid, Spain.
Velázquez-Muriel
Javier A
JA
Luque
Daniel
D
Cuervo
Ana
A
Castón
José R
JR
Valpuesta
José M
JM
Martín-Benito
Jaime
J
Carrascosa
José L
JL
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