Zika virus is a flavivirus which has no vaccines or antiviral medications. Immature flavivirus contains capsid (C), envelope (E), and precursor-membrane (prM) structural proteins. Assembly occurs on the ER membrane; C encloses the positive RNA genome and buds into the ER lumen forming the membrane, and prM/E proteins arrange on the surface. Cryo-EM shows prM/E loops below the membrane; I performed point-mutations on these proteins to investigate the role of internal loops in viral assembly.