The N-Terminal arm of lambda repressor: A proton NMR study.

The N-terminal arm of lambda repressor, which consists of the first six residues, is shown to be flexible in solution by one- and two-dimensional (1)H-NMR methods. In particular, the relaxation of Thr 2 is largely independent of macromolecular tumbling. Also the conformation of the operator-binding domain is not affected by the removal of the first three residues nor by a point mutation, Lys 4 -> Gln. These results support a proposed model of the lambda repressor-operator complex, in which the N-terminal arm of the repressor is assumed to be flexible and to wrap around the operator double helix.