Alternative packing arrangements in the hydrophobic core of lambda repressor

The random alteration of hydrophobic core positions in the N-terminal domain of lambda-repressor, both individually and in combination, shows that there are many ways of repacking the core of the protein. Although the number of functional sequences is limited by constraints on composition, volume and steric interactions, the simple requirement that these positions remain hydrophobic is the main determinant of whether a core sequence is compatible with the wild-type fold.