Premium
lac repressor forms loops with linear DNA carrying two suitably spaced lac operators.
Author(s) -
Krämer H.,
Niemöller M.,
Amouyal M.,
Revet B.,
WilckenBergmann B.,
MüllerHill B.
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.tb02390.x
Subject(s) - repressor , lac repressor , biology , gene , genetics , gene expression
Tetrameric lac repressor may bind to two lac operators on one DNA fragment and induce the intervening DNA to form a loop. Electron microscopy, non‐denaturing polyacrylamide gel electrophoresis, and DNase I protection experiments were used to demonstrate such DNA loops, where the distance between the centres of symmetry of the two lac operators varies between 63 and 535 bp. Formation of a DNA loop is favoured by correct phasing of the two lac operators and a low concentration of both components of the reaction. When a large excess of lac repressor over DNA is used, a ‘tandem’ structure is observed, in which both lac operators are occupied independently by two repressor tetramers. When the concentrations of both lac repressor and lac operator are high, a ‘sandwich’ structure is observed, in which two DNA molecules are connected by two lac repressor tetramers in trans.