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Base sequence‐specific interactions of operator DNA fragments with the lambda‐cro repressor coupled with changes in their conformations.
Author(s) -
Lee S.J.,
Shirakawa M.,
Akutsu H.,
Kyogoku Y.,
Shiraishi M.,
Kitano K.,
Shin M.,
Ohtsuka E.,
Ikehara M.
Publication year - 1987
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 - 10.1002/j.1460-2075.1987.tb04868.x
Subject(s) - dimer , repressor , lambda , dna , base pair , conformational change , stereochemistry , crystallography , biology , denticity , microbiology and biotechnology , biophysics , biochemistry , chemistry , physics , nuclear magnetic resonance , gene , transcription factor , crystal structure , optics
The mechanism of interaction of the operator DNA with the lambda‐cro repressor protein was investigated using proton n.m.r. and photo CIDNP. Three kinds of DNA duplexes, the lambda‐OR3 17‐mer, phi80‐OR2 19‐mer and CRP binding site 22‐mer, were prepared, and all of their imino proton resonances of the complexes with lambda‐cro were assigned to individual base pairs. By monitoring the assigned signals of the DNA fragments and lambda‐cro, it was found that in the complex of lambda‐cro with lambda‐OR3, two subunits of the cro dimer bind to the right and left halves of the OR3, respectively, and the bidentate binding induces a structural distortion in the middle of the 17‐mer. lambda‐cro itself also undergoes a conformational change including loosening of the dimeric form. In the complex of lambda‐cro with phi 80‐OR2, which has a 6‐bp sequence common to that of lambda‐OR3, one subunit of the cro dimer seems to bind specifically to the common part. However, there is only a slight conformational change in the cro dimer. In the mixture of the CRP binding site 22‐mer and lambda‐cro, soft contact without any conformational change was observed between them.