- Nb.BssSI (NEB #R0681) is a derivative of the restriction enzyme BssSI, engineered to possess only one functioning catalytic site. It cleaves the bottom strand of a double-stranded DNA substrate containing the recognition site.
- Nt.BspQI (NEB #R0644) is a derivative of the restriction enzyme BSpQI (NEB #R0712) that cleaves one strand of DNA on a double-stranded DNA substrate.
- Nt.CviPII (NEB #R0626) is a naturally occurring nicking endonuclease cloned from cholorella virus NYs-1.
- Nt.BstNBI (NEB #R0607) is a naturally occurring thermostable nicking endonuclease cloned from Bacillus Stereothermophilus (3,4).
- Nb.BsrDI (NEB #R0648) and Nb.BtsI (NEB #R0707) are naturally occurring large subunits of thermostable heterodimeric enzymes (5).
- Nt.AlwI (NEB #R0627), a derivative of the restriction enzyme AlwI (NEB #R0513) , has been engineered to behave in the same way (6). Both nick just outside their recognition sequences.
- Nb.BbvCI (NEB #R0631) and Nt.BbvCI (NEB #R0632) are alternative derivatives of the heterodimeric restriction enzyme BbvCI, each engineered to possess only one functioning catalytic site (7). These two enzymes nick within the recognition sequence but on opposite strands.
- Nb.BsmI (NEB #R0706) is a bottom-strand specific variant of BsmI (NEB #R0134) discovered from a library of random mutants (8,9).
Nicking endonucleases are as simple to use as restriction endonucleases. Since the nicks generated by 6- or 7-base nicking endonucleases do not fragment DNA, their activities are monitored by conversion of supercoiled plasmids to open circles. Alternatively, substrates with nicking sites close enough on opposite strands to create a double-stranded cut can be used instead.
We are continuing to engineer more nicking enzymes, particularly in response to specific customer needs and applications.