Terminase enzymes mediate the packaging viral DNA into an empty procapsid in a process called DNA packaging and are composed of a heterotrimeric complex of a large subunit (TerL, gpA) and the small subunit (TerS, gpNu1) (TerL-TerS2). TerL contains all the catalytic activities required for for DNA maturation and packaging. At the N-terminal reside the DNA translocase (packaging) and ATPase activities, while at the C-terminal resides the DNA maturation (nuclease/helicase) catalytic activity [1,2,3]. This entry represents the endonuclease domain found at the C-terminal of Terminase large subunit (GpA) from Bacteriophage lambda, which excises an individual genome from the concatemer at the cos site [1,2,3,4].

1: Evidence that a catalytic glutamate and an 'Arginine Toggle' act in concert to mediate ATP hydrolysis and mechanochemical coupling in a viral DNA packaging motor. Ortiz D, delToro D, Ordyan M, Pajak J, Sippy J, Catala A, Oh CS, Vu A, Arya G, Feiss M, Smith DE, Catalano CE; Nucleic Acids Res. 2019;47:1404-1415. PMID:30541105

2: The enzymology of a viral genome packaging motor is influenced by the assembly state of the motor subunits. Andrews BT, Catalano CE; Biochemistry. 2012;51:9342-9353. PMID:23134123

3: The DNA maturation domain of gpA, the DNA packaging motor protein of bacteriophage lambda, contains an ATPase site associated with endonuclease activity. Ortega ME, Gaussier H, Catalano CE; J Mol Biol. 2007;373:851-865. PMID:17870092

4: Walker-A Motif Acts to Coordinate ATP Hydrolysis with Motor Output in Viral DNA Packaging. delToro D, Ortiz D, Ordyan M, Sippy J, Oh CS, Keller N, Feiss M, Catalano CE, Smith DE; J Mol Biol. 2016;428:2709-2729. PMID:27139643