Terminase small subunit

UniProtKB accession:  P03707

Grouped By:  Matching UniProtKB accession

UniProtKB description:  The small subunit is responsible for the binding to multiple recognition elements within the packaging initiation site cos (PubMed:15755448, PubMed:16618107, PubMed:2989542). 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 (binding to packaging sequence cos), and a large terminase subunit possessing endonucleolytic, ATPase and helicase activities (DNA maturation and packaging) (Probable). The terminase binds, cooperatively with the host factor IHFA/IHFB, to the cos site at the junction of adjacent viral genomes in the concatemeric DNA (PubMed:16618107). The endonuclease and helicase activities of the large subunit cleave the viral DNA generating 5'overhangs of 12 bp in length (Probable). The terminase remains bound to the left end of the genome to be packaged, forming a stable DNA-terminase complex (Probable). In a reaction facilitated by the viral assembly catalyst gpFI, the DNA-terminase complex binds to the portal of the procapsid and the terminase packages the viral DNA into the procapsid until the next cos site on the concatemer reaches the complex (Probable). The downstream cos site is then cut generating the mature right end of the genome, the heterotrimer undocks from the DNA-filled head and remains bound to the left end of concatemer's next genome (Probable).