Plays several roles during the time course of infection, including egress of virus particles from the perinuclear space and secondary envelopment of cytoplasmic capsids that bud into specific trans-Golgi network (TGN)-derived membranes. Oligomerizes. Interacts with MDV019; this interaction mediates MDV019 incorporation to virions. Phosphorylated. Belongs to the herpesviridae UL51 family.