2KCA: GP16

In many bacterial viruses and in certain animal viruses, the double-stranded DNA genome enters and exits the capsid through a portal gatekeeper. We report a pseudoatomic structure of a complete portal system. The bacteriophage SPP1 gatekeeper is composed of dodecamers of the portal protein gp6, the adaptor gp15, and the stopper gp16. The solution structures of gp15 and gp16 were determined by NMR. They were then docked together with the X-ray structure of gp6 into the electron density of the approximately 1-MDa SPP1 portal complex purified from DNA-filled capsids. The resulting structure reveals that gatekeeper assembly is accompanied by a large rearrangement of the gp15 structure and by folding of a flexible loop of gp16 to form an intersubunit parallel beta-sheet that closes the portal channel. This stopper system prevents release of packaged DNA. Disulfide cross-linking between beta-strands of the stopper blocks the key conformational changes that control genome ejection from the virus at the beginning of host infection.
PDB ID: 2KCADownload
MMDB ID: 72988
PDB Deposition Date: 2008/12/18
Updated in MMDB: 2016/08
Experimental Method:
solution nmr
Source Organism:
Similar Structures:
Biological Unit for 2KCA: monomeric; determined by author
Molecular Components in 2KCA
Label Count Molecule
Protein (1 molecule)
Bacteriophage Spp1 Complete Nucleotide Sequence(Gene symbol: SPP1p026)
Molecule annotation
* Click molecule labels to explore molecular sequence information.

Citing MMDB