2X53: Structure of the phage p2 baseplate in its activated conformation with Sr

Siphoviridae is the most abundant viral family on earth which infects bacteria as well as archaea. All known siphophages infecting gram+ Lactococcus lactis possess a baseplate at the tip of their tail involved in host recognition and attachment. Here, we report analysis of the p2 phage baseplate structure by X-ray crystallography and electron microscopy and propose a mechanism for the baseplate activation during attachment to the host cell. This approximately 1 MDa, Escherichia coli-expressed baseplate is composed of three protein species, including six trimers of the receptor-binding protein (RBP). RBPs host-recognition domains point upwards, towards the capsid, in agreement with the electron-microscopy map of the free virion. In the presence of Ca(2+), a cation mandatory for infection, the RBPs rotated 200 degrees downwards, presenting their binding sites to the host, and a channel opens at the bottom of the baseplate for DNA passage. These conformational changes reveal a novel siphophage activation and host-recognition mechanism leading ultimately to DNA ejection.
PDB ID: 2X53Download
MMDB ID: 80074
PDB Deposition Date: 2010/2/5
Updated in MMDB: 2011/05
Experimental Method:
x-ray diffraction
Resolution: 3.9  Å
Source Organism:
Similar Structures:
Biological Unit for 2X53: 54-meric; determined by author and by software (PISA)
Molecular Components in 2X53
Label Count Molecule
Proteins (54 molecules)
Molecule annotation
Putative Receptor Binding Protein
Molecule annotation
Molecule annotation
Chemicals (12 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB