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Grabbing the Cat by the Tail: Discrete Steps by a DNA Packaging Motor and their Inter-Subunit Coordination in a Ring-ATPase

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Air date: Wednesday, September 7, 2011, 3:00:00 PM
Time displayed is Eastern Time, Washington DC Local
Views: Total views: 170 * This only includes stats from October 2011 and forward.
Category: WALS - Wednesday Afternoon Lectures
Runtime: 01:10:39
Description: As part of their infection cycle, many viruses must package their newly replicated genomes inside a protein capsid to insure its proper transport and delivery to other host cells. Bacteriophage phi29 packages its 6.6 mm long double-stranded DNA into a 42 nm dia. x 54 nm high capsid using a multimeric ring motor that belongs to the ASCE (Additional Strand, Conserved E) superfamily of ATPases.

A number of fundamental questions remain as to the coordination of the various subunits in these multimeric rings. The portal motor in phi29 is ideal to investigate these questions. Using optical tweezers, we find that this motor can work against loads of up to ~57 picoNewtons on average, making it one of the strongest molecular motors ever reported. Interestingly, the packaging rate decreases as the prohead is filled, indicating that an internal pressure builds up due to DNA compression. The capsid pressure at the end of the packaging is ~6 MegaPascals, corresponding to an internal force of ~52 pN acting on the motor.

We have identified where in the mechanochemical cycle the chemical energy of ATP is converted into mechanical work. Using ultra-high resolution optical tweezers, we have performed the first direct measurement of the step size of a translocating ring ATPase. What emerges is a surprising mechanism that involves a step size with a non-integer number of base pairs and that reveals an unexpected degree of coordination among the individual subunits that has not been proposed previously for a ring ATPase.

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NLM Title: Grabbing the cat by the tail : discrete steps by a DNA packaging motor and their inter-subunit coordination in a ring-ATPase [electronic resource] / Carlos J. Bustamante.
Series: Discrete steps by a DNA packaging motor and their inter-subunit coordination in a ring-ATPase
Author: Bustamante, Carlos.
National Institutes of Health (U.S.)
Publisher:
Other Title(s): Discrete steps by a DNA packaging motor and their inter-subunit coordination in a ring-ATPase
Abstract: (CIT): As part of their infection cycle, many viruses must package their newly replicated genomes inside a protein capsid to insure its proper transport and delivery to other host cells. Bacteriophage phi29 packages its 6.6 mm long double-stranded DNA into a 42 nm dia. x 54 nm high capsid using a multimeric ring motor that belongs to the ASCE (Additional Strand, Conserved E) superfamily of ATPases. A number of fundamental questions remain as to the coordination of the various subunits in these multimeric rings. The portal motor in phi29 is ideal to investigate these questions. Using optical tweezers, we find that this motor can work against loads of up to ~57 picoNewtons on average, making it one of the strongest molecular motors ever reported. Interestingly, the packaging rate decreases as the prohead is filled, indicating that an internal pressure builds up due to DNA compression. The capsid pressure at the end of the packaging is ~6 MegaPascals, corresponding to an internal force of ~52 pN acting on the motor. We have identified where in the mechanochemical cycle the chemical energy of ATP is converted into mechanical work. Using ultra-high resolution optical tweezers, we have performed the first direct measurement of the step size of a translocating ring ATPase. What emerges is a surprising mechanism that involves a step size with a non-integer number of base pairs and that reveals an unexpected degree of coordination among the individual subunits that has not been proposed previously for a ring ATPase.
Subjects: Adenosine Triphosphatases--physiology
Bacteriophages--genetics
DNA Packaging
Genome, Viral
Virus Assembly--genetics
Publication Types: Lectures
Webcasts
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Caption Text: Download Caption File
NLM Classification: QW 161
NLM ID: 101569752
CIT Live ID: 10500
Permanent link: https://videocast.nih.gov/launch.asp?16822

 

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