The maturation protein is required for the typical attachment of the phage to the side of the bacterial pili (PubMed:23810697). Binds to sequences located toward each end of the genome, hence circularizing it (PubMed:26608810). The RNA genome-maturation protein A complex is released from the capsid upon host receptor binding (PubMed:23810697). Maturation protein A enters the cell along with the viral RNA (PubMed:4551992). Interacts with the host pilus. A single copy of the maturation protein is present in the virion. During internalization, MP is proteolytically cleaved into two fragments allowing translation and replication to start. Belongs to the Levivirus maturation protein family.