Kelsey D E, Rounds T C, York S S
Proc Natl Acad Sci U S A. 1979 Jun;76(6):2649-53. doi: 10.1073/pnas.76.6.2649.
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.
N-（碘乙酰氨基乙基）-1-萘胺-5-磺酸盐与大肠杆菌乳糖阻遏物反应，用荧光性的N-（乙酰氨基乙基）-1-萘胺-5-磺酸盐基团选择性标记半胱氨酸-140。当标记的阻遏物与聚[d（A-T）]结合时，该标记的荧光强度降低20%。每个阻遏物四聚体需要15个聚[d（A-T）]碱基对才能完成这种降低。停流实验表明，阻遏物在与聚[d（A-T）]结合时至少经历两种构象变化，半衰期分别为5.0±1.2毫秒和3.5±1.0秒。很可能，这些构象变化有助于加强阻遏物与DNA的相互作用。
