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DenA (Endonuclease II) is a GIY-YIG superfamily DNA endonuclease that initiates degradation of unmodified cytosine-containing host DNA during T4 infection.
"**DenA (Endonuclease II; EndoII)** is a phage-encoded, sequence-context-sensitive DNA endonuclease of the **GIY–YIG nuclease superfamily** that initiates degradation (“restriction”) of **cytosine-containing, unmodified host DNA** during T4 infection."
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EndoII forms an active homotetramer that simultaneously binds two dsDNA molecules.
"Lagerbäck et al. show that EndoII behaves unusually among many GIY–YIG enzymes by forming an active **tetrameric** DNA complex that can bind **two DNA molecules** at once"
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EndoII initiates host chromosomal DNA attack to supply nucleotides for T4 genome synthesis.
"DenA/EndoII is positioned at the **initiation step** of T4 host DNA degradation, producing rare nicks in host DNA that enable further processing."
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Glu118 is a catalytic-surface residue implicated in catalysis and DNA complex stability.
"A catalytic-surface residue **E118** is implicated in catalysis and also affects DNA binding: the **E118A** variant can bind stably as monomer/dimer to a single DNA substrate"