Related Experiment Video
Updated: Oct 7, 2026

Atomic Force Microscopy Investigations of DNA Lesion Recognition in Nucleotide Excision Repair
Published on: May 24, 2017
The nicking endonuclease N.BstNBI is closely related to type IIs restriction endonucleases MlyI and PleI
L S Higgins1, C Besnier, H Kong
1New England Biolabs, 32 Tozer Road, Beverly, MA 01915, USA.
Abstract:
N.BstNBI is a nicking endonuclease that recognizes the sequence GAGTC and nicks the top strand preferentially. The Type IIs restriction endonucleases PleI and MlyI also recognize GAGTC, but cleave both DNA strands. Cloning and sequencing the genes encoding each of these three endonucleases discloses significant sequence similarities. Mutagenesis studies reveal a conserved set of catalytic residues among the three endonucleases, suggesting that they are closely related to each other. Furthermore, PleI and MlyI contain a single active site for DNA cleavage. The results from cleavage assays show that the reactions catalyzed by PleI and MlyI are sequential two step processes. The double-stranded DNA is first nicked on one DNA strand and then further cleaved on the second strand to form linear DNA. Gel filtration analysis shows that MlyI dimerizes in the presence of a cognate DNA and Ca(2+) whereas N.BstNBI remains a monomer, implicating dimerization as a requisite for the second strand cleavage. We suggest that N.BstNBI, MlyI and PleI diverged from a common ancestor and propose that N.BstNBI differs from MlyI and PleI in having an extremely limited second strand cleavage activity, resulting in a site-specific nicking endonuclease.
Related Concept Videos
Restriction Enzymes
The host bacteria protect their own genomic DNA from these enzymes by methylating these sites. Some...
DNA Topoisomerases
Types and Mechanism of action
Topoisomerases are divided into two main types. Type I...
Single-Strand DNA Binding Proteins
Non-LTR Retrotransposons
Homologous Recombination
CRISPR and crRNAs
The CRISPR-Cas system stores a copy of foreign DNA in the host genome and uses it to identify the foreign DNA upon reinfection. CRISPR-Cas has three different...

