The outer protein coat of FMD virus is made up of 60 copies each of the four proteins 1A (VP4), 1B (VP2), 1C (VP3) and 1D (VP1). These four proteins assemble to form a protein sub-unit or protomer. Five protomers join to form a pentamer. Twelve pentamers join up to enclose a strand of RNA and so create a virus particle. The structure thus created has 5, 3 and 2 fold axes of symmetry.