推 Bigfatty73:Lipid membrane underneath the capsid? 12/24 12:51
→ fizeau:I don't know....I try to parahprase the paper 12/24 13:00
→ fizeau:or too many special terms tangled together distract 12/24 13:01
Cell, Vol. 98, 825-833, September 17, 1999.
Viral Evolution Revealed by Bacteriophage PRD1
and Human Adenovirus Coat Protein Structures
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Summary
The unusual bacteriophage PRD1 features a membrane beneath its icosahedral
protein coat. The crystal structure of the major coat protein P3 reveals a
molecule with three interlocking subunits. Surprisingly the P3 molecule
closely resembles hexon, the equivalent protein in human adenovirus.
Introduction
The dsDNA bacteriophage PRD1 was discovered in the sewers of Kalamazoo,
Michigan, in the 1970s. It is the prototypic example of Tectiviridae, with
virions characterized by their unusual possession of an internal membrane
that lies beneath the icosahedral protein capsid.
PRD1 is also an unusual bacteriophage because it does not have a tail, as
do the other dsDNA bacteriophages, but uses its membrane to "inject" the
genome into the bacterium. The viral membrane is aquired during assembly
from the host. An area of the bacterial plasma membrane, which contains
virus-specific membrane proteins, buds into the cytosol and acts as a
scaffold for the assembly of the coat proteins to form the procapsid. Image
reconstructions from cryoelectron micrographs of complete virions and
procapsids from a mutant strain which is unable to package the genome, show
that both have the same diameters. Thus there is no capsid expansion nor
are there changes in the capsomer proteins upon maturation when the genome is
packaged into the empty PRD1 capsids, but structural rearrangements do occur
in the membrane. This maturation machanism is quite unlike that for most
other dsDNA bacteriophages, which exhibit considerable changes in their capsid
size and organization on genome packaging.
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