Modulation of the Viral ATPase Activity by the Portal Protein Correlates with DNA Packaging Efficiency

Leonor Oliveira,Adriano O Henriques,Paulo Tavares

doi:10.1074/jbc.m603314200

Abstract

DNA packaging in tailed bacteriophages and herpesviruses requires assembly of a complex molecular machine at a specific vertex of a preformed procapsid. As in all these viruses, the DNA translocation motor of bacteriophage SPP1 is composed of the portal protein (gp6) that provides a tunnel for DNA entry into the procapsid and of the viral ATPase (gp1-gp2 complex) that fuels DNA translocation. Here we studied the cross-talk between the components of the motor to control its ATP consumption and DNA encapsidation. We showed that gp6 embedded in the procapsid structure stimulated more than 10-fold the gp2 ATPase activity. This stimulation, which was significantly higher than the one conferred by isolated gp6, depended on the presence of gp1. Mutations in different regions of gp6 abolished or decreased the gp6-induced stimulation of the ATPase. This effect on gp2 activity was observed both in the presence and in the absence of DNA and showed a strict correlation with the efficiency of DNA packaging into procapsids containing the mutant portals. Our results demonstrated that the portal protein has an active control over the viral ATPase activity that correlates with the performance of the DNA packaging motor.

Highlights

The mechanism by which viral DNA is packaged into a preformed procapsid is a fascinating but still unsolved biological problem
Our results demonstrated that the portal protein has an active control over the viral ATPase activity that correlates with the performance of the DNA packaging motor
Concluding Remarks—The results described in this paper strongly suggested that the portal protein plays an essential role to control ATP hydrolysis by the terminase to levels compatible with viral DNA translocation

Summary

Introduction

The mechanism by which viral DNA is packaged into a preformed procapsid is a fascinating but still unsolved biological problem. Tailed phages and herpesviruses package DNA to densities as high as 500 mg/ml in the preformed procapsid structure [1,2,3]. The motor is composed of an ATPase (terminase) and of the portal protein, a turbine-like oligomer localized at the unique vertex of the icosahedral capsid through which DNA movements occur [7,8,9,10,11]. DNA is translocated through the central tunnel of the oligomeric portal protein to be packed at high density inside the viral capsid. The packaging reaction requires substrate DNA, ATP, the terminase gp1-gp complex, and procapsids with the portal protein gp. Regulation of the viral ATPase activity by the portal protein in the assembled DNA translocation motor appeared essential for the mechanism of viral genome packaging

Results

Discussion

Conclusion