Clement R, Daune MP. Binding of lactose repressor to poly d(A-T) : OD AND CD melting of the complex.
Nucleic Acids Res 1975;
2:303-18. [PMID:
1093136 PMCID:
PMC342837 DOI:
10.1093/nar/2.3.303]
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Abstract
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.
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