This is the C-terminal domain of a family of eumetazoan proteins collectively defined as calmodulin-regulated spectrin-associated, or CAMSAP, proteins. CAMSAP proteins carry an N-terminal region that includes the CH domain, a central region including a predicted coiled-coil and this C-terminal, or CKK, domain - defined as being present in CAMSAP, KIAA1078 and KIAA1543, The C-terminal domain is the part of the CAMSAP proteins that binds to microtubules. The domain appears to act by producing inhibition of neurite extension, probably by blocking microtubule function. CKK represents a domain that has evolved with the metazoa. The structure of a murine hypothetical protein from RIKEN cDNA has shown the domain to adopt a mainly beta barrel structure with an associated alpha-helical hairpin.