The glutamate switch of bacteriophage T7 DNA helicase: role in coupling nucleotide triphosphate (NTP) and DNA binding to NTP hydrolysis.

ABSTRACT: The DNA helicase encoded by gene 4 of bacteriophage T7 forms a hexameric ring in the presence of dTTP, allowing it to bind DNA in its central core. The oligomerization also creates nucleotide-binding sites located at the interfaces of the subunits. DNA binding stimulates the hydrolysis of dTTP but the mechanism for this two-step control is not clear. We have identified a glutamate switch, analogous to the glutamate switch found in AAA+ enzymes that couples dTTP hydrolysis to DNA binding. A crystal structure of T7 helicase shows that a glutamate residue (Glu-343), located at the subunit interface, is positioned to catalyze a nucleophilic attack on the γ-phosphate of a bound nucleoside 5'-triphosphate. However, in the absence of a nucleotide, Glu-343 changes orientation, interacting with Arg

SUBMITTER: Satapathy AK 

PROVIDER: S-EPMC3123078 | biostudies-literature | 2011 Jul

REPOSITORIES: biostudies-literature