Involved in urease metallocenter assembly. Binds nickel. Probably functions as a nickel donor during metallocenter assembly. Binds 1 Zn(2+) or 1 Ni(2+) ion per dimer or tetramer. Homodimer in diluted solutions, homotetramer in concentrated solutions and when bound to Ni(2+) or Zn(2+). The homodimer is thought to be the active form. Belongs to the UreE family.