| Primary Identifier | IPR005021 | Type | Family |
| Short Name | Terminase_largesu-like |
| description | Terminase large subunit (TerL) from bacteriophages and evolutionarily related viruses, is an important component of the DNA packing machinery and comprises an ATPase domain, which powers DNA translocation and a nuclease domain that cuts concatemeric DNA [, , ]. TerL forms pentamers in which the ATPase domains form a ring distal to the capsid. The ATPase domain contains a C-terminal subdomain that sits above the ATPase active site, called the "Lid subdomain"with reference to analogous lid subdomains found in other ATPases []. It contains a hydrophobic patch (Trp and Tyr residues) that mediates critical interactions in the interface between adjacent ATPase subunits and assists the positioning of the arginine finger residue that catalyses ATP hydrolysis []. The endonuclease cuts concatemeric DNA first in the initiation phase in a sequence specific site and later in the completion stage of the DNA packaging process when the capsid is full [, ]. Cryo-EM studies indicate that TerL forms a pentamer that binds to a dodecameric assembly called portal and attaches to the capsid. It has been proposed that nuclease domains form a radially arranged ring that is proximal to portal, playing a key role in pentamer assembly []. The nuclease domain has a RNAse H-like fold and it has been proposed to utilise a two-metal catalysis mechanism like in other RNAse H-like endonucleases such as RNase H, transposases, retroviral integrases and RuvC Holliday junction resolvases []. This entry also includes uncharacterised bacterial sequences. |
