The chromodomain is a conserved region of about 50 amino acids, found in a variety of chromosomal proteins. The chromodomain is implicated in the binding, of the proteins in which it is found, to methylated histone tails and maybe RNA. A chromodomain may occur as a single instance, in a tandem arrangement, or followed by a related chromo shadow domain. Chromodomains belong to the chromo-like superfamily of SH3-fold-beta-barrel domains which includes chromo shadow domains and chromo barrel domains. Chromodomains differ from these in that they lack the first strand of the SH3-fold-beta-barrel. This first strand is altered by insertion in the chromo shadow domains, and chromo barrel domains are typical SH3-fold-beta-barrel domains with sequence similarity to the canonical chromo domain.