Evidence for an electrostatic mechanism of force generation by the bacteriophage T4 DNA packaging motor

• Published in: Nature communications Vol. 5; no. 1; p. 4173
• Main Authors: Migliori, Amy D., Keller, Nicholas, Alam, Tanfis I., Mahalingam, Marthandan, Rao, Venigalla B., Arya, Gaurav, Smith, Douglas E.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 17-06-2014; Nature Publishing Group
• Subjects: 631/326/1321; 631/45/535; 631/57/2272; 631/57/343/2280; Adenosine Triphosphate - metabolism; Bacteriophage T4 - physiology; Biomechanical Phenomena; Crystal structure; DNA Packaging - physiology; Energy; Humanities and Social Sciences; Hydrolysis; Models, Biological; Models, Molecular; Molecular Dynamics Simulation; Molecular Motor Proteins - physiology; multidisciplinary; Mutagenesis; Mutagenesis, Site-Directed; Mutation; Science; Science (multidisciplinary); Static Electricity; Viral Proteins - chemistry; Viral Proteins - physiology; La Jolla California; United States > US; California
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms5173

How viral packaging motors generate enormous forces to translocate DNA into viral capsids remains unknown. Recent structural studies of the bacteriophage T4 packaging motor have led to a proposed mechanism wherein the gp17 motor protein translocates DNA by transitioning between extended and compact states, orchestrated by electrostatic interactions between complimentarily charged residues across the interface between the N- and C-terminal subdomains. Here we show that site-directed alterations in these residues cause force dependent impairments of motor function including lower translocation velocity, lower stall force and higher frequency of pauses and slips. We further show that the measured impairments correlate with computed changes in free-energy differences between the two states. These findings support the proposed structural mechanism and further suggest an energy landscape model of motor activity that couples the free-energy profile of motor conformational states with that of the ATP hydrolysis cycle.
Viral DNA packaging motors must generate large forces to package the viral capsid. Here, Migliori
et al.
provide functional and computational evidence that electrostatic interactions between subdomains of the T4 packaging motor provide the driving force for DNA packaging.