Hox proteins have a sequence in common

Sequences of fly homeodomains. All eight Drosophila Hox genes encode proteins containing a highly conserved 60 amino acid domain, the homeodomain, composed of three α helices. Helices 2 and 3 form a helix-turn-helix motif similarly to the Lac repressor, Cro, and other DNA-binding proteins. Residues common to the Hox genes are shaded in yellow; divergent residues are shaded in red; those common to subsets of proteins are shaded in blue or green.

[S. B. Carroll, J. K. Grenier, and S. D. Weatherbee, From DNA to Diversity: Molecular Genetics and the Evolution of Animal Design, 2nd ed. Blackwell, 2005.]