title: An ATP hydrolysis sensor in the DNA packaging motor from bacteriophage T4 suggests an inchworm-type translocation mechanism.
abstract: Tailed bacteriophages and large eukaryotic viruses employ powerful molecular motors to translocate dsDNA into a preassembled capsid shell. The phage T4 motor is composed of a dodecameric portal and small and large terminase subunits assembled at the special head-tail connector vertex of the prohead. The motor pumps DNA through the portal channel, utilizing ATP hydrolysis energy provided by an ATPase present in the large terminase subunit. We report that the ATPase motors of terminases, helicases, translocating restriction enzymes, and protein translocases possess a common coupling motif (C-motif). Mutations in the phage T4 terminase C-motif lead to loss of stimulated ATPase and DNA translocation activities. Surprisingly, the mutants can catalyze at least one ATP hydrolysis event but are unable to turn over and reset the motor. This is the first report of a catalytic block in translocating ATPase motor after ATP hydrolysis occurred. We suggest that the C-motif is an ATP hydrolysis sensor, linking product release to mechanical motion. A novel terminase-driven mechanism is proposed for translocation of dsDNA in viruses.
authors.affiliation: Department of Biology, The Catholic University of America, Washington, DC 20064, USA.
authors.forename: Bonnie
authors.initials: B
authors.lastname: Draper
authors.forename: Venigalla B
authors.initials: VB
authors.lastname: Rao
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism*; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D017122:Bacteriophage T4 / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*; D001692:Biological Transport; D002384:Catalysis; D042003:DNA Packaging; D004279:DNA, Viral / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D003851:Deoxyribonucleases / Q000378:metabolism; D004706:Endodeoxyribonucleases / Q000737:chemistry; D019143:Evolution, Molecular; D006868:Hydrolysis; D008958:Models, Molecular; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000378:metabolism; D011485:Protein Binding; D014764:Viral Proteins / Q000378:metabolism
chemical_list: D004279:DNA, Viral; D004268:DNA-Binding Proteins; C065037:Gp16 protein, Bacteriophage T4; D050505:Mutant Proteins; D014764:Viral Proteins; C069680:bacteriophage T7 leg protein gp17; D000255:Adenosine Triphosphate; D003851:Deoxyribonucleases; D004706:Endodeoxyribonucleases; C104812:terminase, phage T4; D000251:Adenosine Triphosphatases