Old, new, and widely true: The bacteriophage T4 DNA packaging mechanism.
DNA packaging into empty viral procapsids by ATP-driven motor proteins applies widely among viruses. Recent fluorescence studies of phage T4 reveal: 1) the small terminase subunit (TerS) synapses pac homologs by a twin ring mechanism to gauge DNA maturation and allow packaging by the large terminase subunit (TerL); 2) translocation of linear DNA is efficient by TerL acting alone; expansion of the procapsid is controlled by the portal-terminase assembly; 3) both ends of the packaged DNA are held at the portal, showing a loop of DNA is packaged; 4) transient spring-like compression of B form to A form-like DNA accompanies translocation; 5) the C-terminal domain of TerL is docked to the portal and moves toward it when stalled; 6) a portal bound resolvase can release stalled Y-DNA compression and allow translocation in vitro; and 7) ATP powered translocation on A form dsDNA is supported by recent hexameric helicase studies.
Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, 108N. Greene Street, Baltimore, MD 21201, USA. Electronic address: lblack@umaryland.edu.
Lindsay W
LW
Black
D017122:Bacteriophage T4 / Q000502:physiology*; D042003:DNA Packaging; D004279:DNA, Viral / Q000378:metabolism*; D008954:Models, Biological; D014764:Viral Proteins / Q000378:metabolism*
D004279:DNA, Viral; D014764:Viral Proteins
A form DNA; DNA motors; DNA packaging; Helicase; Pac site; Terminase