Open Accesslac repressor changes conformation upon binding to poly[dA-T)]
Author(s) -
David E. Kelsey,
Thomas C. Rounds,
Sheldon S. York
Publication year - 1979
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.76.6.2649
Subject(s) - repressor , tetramer , chemistry , dna , lac repressor , escherichia coli , fluorescence , stereochemistry , biochemistry , gene , gene expression , physics , quantum mechanics , enzyme
N-(Iodoacetylaminoethyl)-1-naphthylamine-5-sulfonate reacts with Escherichia coli lac repressor to selectively label cysteine-140 with the fluorescent N-(acetylaminoethyl)-1-naphthylamine-5-sulfonate group. The fluorescence intensity of this label decreases by 20% when labeled repressor associates with poly[d(A-T)]. Fifteen base pairs of poly[d(A-T)] per repressor tetramer are required to complete this decrease. Stopped-flow experiments have shown that the repressor undergoes at least two conformational changes as it binds to poly[d(A-T)], with half-lives of 5.0 +/- 1.2 msec and 3.5 +/- 1.0 sex. Quite likely, these conformational changes serve to strengthen the interaction of repressor with DNA.