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McrB s , a modulator peptide for McrBC activity
Author(s) -
Panne Daniel,
Raleigh Elisabeth A.,
Bickle Thomas A.
Publication year - 1998
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/17.18.5477
Subject(s) - biology , cleavage (geology) , dna , gtp' , biochemistry , gene , microbiology and biotechnology , enzyme , paleontology , fracture (geology)
McrBC is a methylation‐dependent endonuclease from Escherichia coli K‐12. The enzyme recognizes DNA with modified cytosines preceded by a purine. McrBC restricts DNA that contains at least two methylated recognition sites separated by 40–80 bp. Two gene products, McrB L and McrB s , are produced from the mcrB gene and one, McrC, from the mcrC gene. DNA cleavage in vitro requires McrB L , McrC, GTP and Mg 2+ . We found that DNA cleavage was optimal at a ratio of 3–5 McrB L per molecule of McrC, suggesting that formation of a multisubunit complex with several molecules of McrB L is required for cleavage. To understand the role of McrB s , we have purified the protein and analyzed its role in vitro . At the optimal ratio of 3–5 McrB L per molecule of McrC, McrB s acted as an inhibitor of DNA cleavage. Inhibition was due to sequestration of McrC and required the presence of GTP, suggesting that the interaction is GTP dependent. If McrC was in excess, a condition resulting in suboptimal DNA cleavage, addition of McrB s enhanced DNA cleavage, presumably due to sequestration of excess McrC. We suggest that the role of McrB s is to modulate McrBC activity by binding to McrC.