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. 1979 Jun;76(6):2649-53.
doi: 10.1073/pnas.76.6.2649.

lac repressor changes conformation upon binding to poly[dA-T)]

D E Kelsey, T C Rounds, S S York

lac repressor changes conformation upon binding to poly[dA-T)]

D E Kelsey et al. Proc Natl Acad Sci U S A. 1979 Jun.

Abstract

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.

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References

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