Clement R, Daune M P
Nucleic Acids Res. 1975 Mar;2(3):303-18. doi: 10.1093/nar/2.3.303.
The binding of lactose repressor to poly d(A-T) at low ionic strength has been investigated by heat denaturation. The poly d(A-T) melting is monitored by optical density and the protein melting by circular dichroism. From the modification of the poly d(A-T) melting curve we estimate a maximum binding ratio of about one tetrameric repressor to about 20 basic pairs. The repressor melting can be interpreted as a global shift from a to b structure of about 25 residues per subunit. The melting curves of poly d(A-T) and repressor have not a shape easy to interpret; nevertheless both show a cooperative transition in the same temperature range where we can evaluate that about 3.8 aminoacid residues shift from a to b structure when 1 bases pair melt.
通过热变性研究了低离子强度下乳糖阻遏物与聚d(A-T)的结合。通过光密度监测聚d(A-T)的解链,通过圆二色性监测蛋白质的解链。根据聚d(A-T)解链曲线的变化,我们估计最大结合比约为一个四聚体阻遏物与约20个碱基对结合。阻遏物的解链可解释为每个亚基约25个残基从a结构到b结构的整体转变。聚d(A-T)和阻遏物的解链曲线形状不易解释;然而,两者在相同温度范围内均显示出协同转变,在此温度范围内我们可以评估出当1个碱基对解链时约3.8个氨基酸残基从a结构转变为b结构。