Highly efficient protein <i>trans</i>‐splicing by a naturally split DnaE intein from <i>Nostoc punctiforme</i>

Protein trans-splicing by the naturally split intein of the gene dnaE from Nostoc punctiforme (Npu DnaE) was demonstrated here with non-native exteins in Escherichia coli. Npu DnaE possesses robust trans-splicing activity with an efficiency of > 98%, which is superior to that of the DnaE intein from Synechocystis sp. strain PCC6803 (Ssp DnaE). Both the N- and C-terminal parts of the split Npu DnaE intein can be substituted with the corresponding fragment of Ssp DnaE without loss of trans-splicing activity. Protein splicing with the Npu DnaEN is also more tolerant of amino acid substitutions in the C-terminal extein sequence.