Internal capsid protein that is probably ejected along with the viral DNA and prevents degradation of viral DNA by the host type I restriction-modification antiviral defense system (PubMed:3029954). Plays a role in directing proper capsid assembly (PubMed:28509398). Internal capsid protein. A proteolytically cleaved 60 kDa form is incorporated into the virion. Expressed late in the viral replication cycle. Proteolytically cleaved into a 60 kDa form which is incorporated into the virion. Phage P1 Dar antirestriction system is composed of Hdf, DarA, DdrA, DdrB, DarB and Ulx. Hdf and DarA are incorporated first in the procapsid in a co-dependent manner, followed by DarB, DdrB and Ulx.