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The nuclease domain of the SPP1 packaging motor coordinates DNA cleavage and encapsidation.


ABSTRACT: The large terminase subunit is a central component of the genome packaging motor from tailed bacteriophages and herpes viruses. This two-domain enzyme has an N-terminal ATPase activity that fuels DNA translocation during packaging and a C-terminal nuclease activity required for initiation and termination of the packaging cycle. Here, we report that bacteriophage SPP1 large terminase (gp2) is a metal-dependent nuclease whose stability and activity are strongly and preferentially enhanced by Mn(2+) ions. Mutation of conserved residues that coordinate Mn(2+) ions in the nuclease catalytic site affect the metal-induced gp2 stabilization and impair both gp2-specific cleavage at the packaging initiation site pac and unspecific nuclease activity. Several of these mutations block also DNA encapsidation without affecting ATP hydrolysis or gp2 C-terminus binding to the procapsid portal vertex. The data are consistent with a mechanism in which the nuclease domain bound to the portal switches between nuclease activity and a coordinated action with the ATPase domain for DNA translocation. This switch of activities of the nuclease domain is critical to achieve the viral chromosome packaging cycle.

SUBMITTER: Cornilleau C 

PROVIDER: S-EPMC3592435 | BioStudies | 2013-01-01

REPOSITORIES: biostudies

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