Structural highlights
Function
[TERL_BPSPP] Component of the molecular motor that translocates genomic DNA in empty capsid during DNA packaging. Heterodimerizes with small terminase protein to be docked on capsid portal protein. The latter forms a ring in which genomic DNA in translocated into the capsid. May have or induce an endonuclease activity to cleave the genome concatemer after encapsidation (By similarity).
Evolutionary Conservation
Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.
Publication Abstract from PubMed
The DNA-packaging motor in tailed bacteriophages requires nuclease activity to ensure that the genome is packaged correctly. This nuclease activity is tightly regulated as the enzyme is inactive for the duration of DNA translocation. Here, we report the X-ray structure of the large terminase nuclease domain from bacteriophage SPP1. Similarity with the RNase H family endonucleases allowed interactions with the DNA to be predicted. A structure-based alignment with the distantly related T4 gp17 terminase shows the conservation of an extended beta-sheet and an auxiliary beta-hairpin that are not found in other RNase H family proteins. The model with DNA suggests that the beta-hairpin partly blocks the active site, and in vivo activity assays show that the nuclease domain is not functional in the absence of the ATPase domain. Here, we propose that the nuclease activity is regulated by movement of the beta-hairpin, altering active site access and the orientation of catalytically essential residues.
Structural basis for the nuclease activity of a bacteriophage large terminase.,Smits C, Chechik M, Kovalevskiy OV, Shevtsov MB, Foster AW, Alonso JC, Antson AA EMBO Rep. 2009 Jun;10(6):592-8. Epub 2009 May 15. PMID:19444313[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Smits C, Chechik M, Kovalevskiy OV, Shevtsov MB, Foster AW, Alonso JC, Antson AA. Structural basis for the nuclease activity of a bacteriophage large terminase. EMBO Rep. 2009 Jun;10(6):592-8. Epub 2009 May 15. PMID:19444313 doi:10.1038/embor.2009.53
