Function
The terminase large subunit acts as an ATP driven molecular motor necessary for viral DNA translocation into empty capsids and as an endonuclease that cuts the viral genome to initiate and to end a packaging reaction (Probable). The terminase lies at a unique vertex of the procapsid and is composed of two subunits, a small terminase subunit involved in viral DNA recognition (packaging sequence), and a large terminase subunit possessing endonucleolytic and ATPase activities (By similarity). Both terminase subunits heterooligomerize and are docked on the portal protein to form the packaging machine. The terminase large subunit exhibits endonuclease activity and cleaves the viral genome concatemer once the capsid is full (headful packaging) (By similarity). Once the capsid is packaged with the DNA, the terminase complex is substituted by the tail (By similarity).
Sequence
MKRLRPSDKFFELLGYKPHHVQLAIHRSTAKRRVACLGRQSGKSEAASVEAVFELFARPGSQGWIIAPTYDQAEIIFGRVVEKVERLAEVFPATEVQLQRRRLRLLVHHYDRPVNAPGAKRVATSEFRGKSADRPDNLRGATLDFVILDEAAMIPFSVWSEAIEPTLSVRDGWALIISTPKGLNWFYEFFLMGWRGGLKEGIPNSGVNQTHPDFESFHAASWDVWPERREWYMERRLYIPDLEFRQEYGAEFVSHSNSVFSGLDMLILLPYERRGTRLVVEDYRPDHIYCIGADFGKNQDYSVFSVLDLDTGAIVCLERMNGATWSDQVARLKALSEDYGHAYVVADTWGVGDAIAEELDAQGINYTPLPVKSSSVKEQLISNLALLMEKGQVAVPNDKTILDELRNFRYYRTASGNQVMRAYGRGHDDIVMSLALAYSQYEGKDGYKFELAEERPSKLKHEESVMSLVEDDFTDLELANRAFSA