The present invention relates to nucleic acids encoding the novel parvoviral protein “assembly activating protein” (AAP), the encoded polypeptides, methods of producing the polypeptides, antibodies specific for AAP, the use of the nucleic acids for the preparation of the polypeptides, the use of the nucleic acids or the polypeptides for the preparation of the parvoviral particle and methods of producing parvoviral particles essentially consisting of VP3 by providing in addition to the coding sequence of the parvoviral structural protein VP3 a sequence fragment Z/a nucleic acid encoding AAP in the cell and expressing VP3 and fragment Z under control of a rep-independent promoter. Furthermore, the present invention relates to parvoviral particles essentially consisting of VP3 and/or obtainable by the above method as well as expression cassettes comprising (i) a heterologous promoter and (ii) VP3 coding sequence and/or fragment Z. The present invention further relates to a medicament, particularly a vaccine, comprising the parvoviral particles or expression cassettes and their use.