title: High degree of coordination and division of labor among subunits in a homomeric ring ATPase.
abstract: Ring NTPases of the ASCE superfamily perform a variety of cellular functions. An important question about the operation of these molecular machines is how the ring subunits coordinate their chemical and mechanical transitions. Here, we present a comprehensive mechanochemical characterization of a homomeric ring ATPase-the bacteriophage φ29 packaging motor-a homopentamer that translocates double-stranded DNA in cycles composed of alternating dwells and bursts. We use high-resolution optical tweezers to determine the effect of nucleotide analogs on the cycle. We find that ATP hydrolysis occurs sequentially during the burst and that ADP release is interlaced with ATP binding during the dwell, revealing a high degree of coordination among ring subunits. Moreover, we show that the motor displays an unexpected division of labor: although all subunits of the homopentamer bind and hydrolyze ATP during each cycle, only four participate in translocation, whereas the remaining subunit plays an ATP-dependent regulatory role.
authors.affiliation: Department of Physics and Jason L. Choy Laboratory of Single Molecule Biophysics, University of California, Berkeley, Berkeley, CA 94720, USA.
authors.forename: Gheorghe
authors.initials: G
authors.lastname: Chistol
authors.forename: Shixin
authors.initials: S
authors.lastname: Liu
authors.forename: Craig L
authors.initials: CL
authors.lastname: Hetherington
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Moffitt
authors.forename: Shelley
authors.initials: S
authors.lastname: Grimes
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Jardine
authors.forename: Carlos
authors.initials: C
authors.lastname: Bustamante
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D017103:Bacillus Phages / Q000201:enzymology*; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D006868:Hydrolysis; D008958:Models, Molecular; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism
chemical_list: D021122:Protein Subunits; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D004247:DNA; D000251:Adenosine Triphosphatases