Bacteriophage T4 endonuclease II, a promiscuous GIY-YIG nuclease, binds as a tetramer to two DNA substrates.

ABSTRACT: The oligomerization state and mode of binding to DNA of the GIY-YIG endonuclease II (EndoII) from bacteriophage T4 was studied using gel filtration and electrophoretic mobility shift assays with a set of mutants previously found to have altered enzyme activity. At low enzyme/DNA ratios all mutants except one bound to DNA only as tetramers to two DNA substrates. The putatively catalytic E118 residue actually interfered with DNA binding (possibly due to steric hindrance or repulsion between the glutamate side chain and DNA), as shown by the ability of E118A to bind stably also as monomer or dimer to a single substrate. The tetrameric structure of EndoII in the DNA-protein complex is surprising considering the asymmetry of the recognized sequence and the predominantly single-stranded nicking.

SUBMITTER: Lagerback P 

PROVIDER: S-EPMC2764454 | biostudies-literature | 2009 Oct

REPOSITORIES: biostudies-literature