The current invention pertains to adapters comprising a protelomerase recognition sequence, preferably a TeIN protelomerase recognition sequence. The adapters of the invention can be used for the preparation of a nucleic acid molecule library. The invention also relates to a method for producing a nucleic acid molecule library using one or more adapters comprising a protelomerase recognition sequence. The adapters may be contacted with a protelomerase to cleave and close the ends of the adapters. Said closed adapters are e.g. protected against exonuclease treatment. The method of the invention further concerns an amplification method and a sequencing method using adapters having a protelomerase recognition sequence.