Envelope protein which participates in virus morphogenesis. Needed for an early step in viral crescent membrane formation by interacting with D13 scaffold protein. Its interaction with D13 scaffold protein leads to the formation of rigid, crescent-shaped membranes that assemble around the cytoplasmic virus factory. Membrane anchor for the protein A27. A17-A27 virus envelope protein might be involved in fusion or attachment, and can further associate to A26 (By similarity). Interacts (via N-terminus) with D13 scaffold; this interaction helps D13 to associate with membranes. Interacts with A14. Interacts with A27; this interaction allows A27 to be anchored in the mature virion (MV) membrane. Part of a complex composed of A17, A25, A26 and A27 (By similarity). The 22 kDa precursor is probably cleaved by the I7 protease during virus maturation. Phosphorylated on tyrosine and threonine. Its phosphorylation state is regulated by the F10 kinase and the H1 phosphatase (By similarity). Phosphorylation by F10 kinase seems to be required to form the membranes associated with IV (By similarity). Belongs to the chordopoxvirinae A17 family.