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Purification and characterization of the Ner repressor of bacteriophage Mu
Author(s) -
Kukolj George,
Tolias Peter P.,
DuBow Michael S.
Publication year - 1989
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(89)80565-4
Subject(s) - bacteriophage , repressor , characterization (materials science) , chemistry , biology , biochemistry , escherichia coli , gene , nanotechnology , materials science , transcription factor
The Ner protein of bacteriophage Mu acts as a λ cro‐like negative regulator of the phage's early (transposase) operon. Using the band retardation assay to monitor ner ‐operator‐specific DNA‐binding activity, the 8 kDa Ner protein was purified to homogeneity. DNase I footprinting revealed that the purified protein bound and protected a specific DNA operator that contains two 12 bp sites with the consensus sequence 5′‐ANPyTAPuCTAAGT‐3′, separated by a 6 bp spacer region. Moreover, regions corresponding to a turn of the DNA helix flanking these 12 bp repeats are also protected by Ner. Unlike the functionally similar λ cro protein, gel filtration experiments show the native molecular mass of Mu Ner to be approx. 8 kDa. These results, plus the pattern of DNase I protection, suggest that the protein may bind as a monomer to each of its specific DNA substrates.