The naturally split Npu DnaE intein exhibits an extraordinarily high rate in the protein trans-splicing reaction

We have studied the naturally split αα subunit of the DNA polymerase III (DnaE) intein from Nostoc punctiforme PCC73102 (Npu)   using purified proteins and determined an apparent first-order rate constant of (1.1±0.2)×10-2(1.1±0.2)×10-2 s−1 at 37 °C. This represents the highest rate reported for the protein trans  -splicing reaction so far (t1/2t1/2 of ∼∼ 60 s). Furthermore, the reaction was very robust and high-yielding with respect to different extein sequences, temperatures from 6 to 37 °C, and the presence of up to 6 M urea. Given these outstanding properties, the Npu DnaE intein appears to be the intein of choice for many applications in protein and cellular chemistry.