How does cro repressor recognize its DNA target sites?

The structure of the cro repressor from bacteriophage λ suggests that a pair of α-helices of this gene-regulatory protein bind to its sequence-specific sites on the DNA. These protein α-helices lie within successive major grooves of the DNA, and amino acid side chains make multiple hydrogen bonds with the accessible parts of the DNA base pairs. Each α-helix is part of a common two-helical DNA-binding fold that apparently occurs in many proteins that regulate gene expression.