Late protein which is a part of a large complex required for early virion morphogenesis. This complex participates in the formation of virosomes and the incorporation of virosomal contents into nascent immature virions. J1 protein is required for DNA packaging during immature virions (IV) formation (Probable). Homodimer. Part of a complex composed of A30, G7, F10 kinase, A15, D2, D3, and J1. Interacts with A45. Localizes in cytoplasmic virus factories. Probably located in between the core and the virion membrane. Expressed in the late phase of the viral replicative cycle. Belongs to the chordopoxvirinae J1 family.