NMR Studies of Repressor-Operator Interaction. The Lac Control Region

How do proteins such as repressors recognize specific base pair sequences in DNA? This is one of the most intriguing problems in molecular biology. Some clues have come from the well-known crystallographic studies on cro (Anderson et al. 1981) and lambda repressors (Pabo and Lewis 1982), CAP (McKay and Steitz 1981) and, more recently, trp repressor (Schevitz et al. 1985). All these proteins have a very similar helix-turn-helix structural domain, which is implicated from genetic studies to contain the main determinants for specific DNA recognition (for a review see Pabo and Sauer 1984). Solution of the repressor crystal structures led to a series of model-building studies aimed at modelling the interaction with the DNA binding sites (Anderson et al. 1981; Ohlendorf et al. 1982; Pabo and Lewis 1982; McKay and Steitz 1981; Matthews et al. 1982; Weber et al. 1982).