DNA crunching by a viral packaging motor: Compression of a procapsid-portal stalled Y-DNA substrate.
Many large double-stranded DNA viruses employ high force-generating ATP-driven molecular motors to package to high density their genomes into empty procapsids. Bacteriophage T4 DNA translocation is driven by a two-component motor consisting of the procapsid portal docked with a packaging terminase-ATPase. Fluorescence resonance energy transfer and fluorescence correlation spectroscopic (FRET-FCS) studies of a branched (Y-junction) DNA substrate with a procapsid-anchoring leader segment and a single dye molecule situated at the junction point reveal that the "Y-DNA" stalls in proximity to the procapsid portal fused to GFP. Comparable structure Y-DNA substrates containing energy transfer dye pairs in the Y-stem separated by 10 or 14 base pairs reveal that B-form DNA is locally compressed 22-24% by the linear force of the packaging motor. Torsional compression of duplex DNA is thus implicated in the mechanism of DNA translocation.
Ray
Krishanu
K
Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, 108 N. Greene St., Baltimore, MD 21201, USA. krishanu@cfs.umbi.umd.edu
Sabanayagam
Chandran R
CR
Lakowicz
Joseph R
JR
Black
Lindsay W
LW
D017122:Bacteriophage T4 / Q000502:physiology*; D002213:Capsid / Q000378:metabolism*; D004279:DNA, Viral / Q000378:metabolism*; D005454:Fluorescence Polarization; D031541:Fluorescence Resonance Energy Transfer; D005456:Fluorescent Dyes; D018613:Microscopy, Confocal; D009690:Nucleic Acid Conformation; D019065:Virus Assembly; D014966:Xanthenes
D004279:DNA, Viral; D005456:Fluorescent Dyes; D014966:Xanthenes; C034657:Texas red