This short motif is found in a number of plant proteins. It is rich in basic amino acids and has been called a CCT motif after Co, Col and Toc1 [1]. The CCT motif is about 45 amino acids long and contains a putative nuclear localisation signal within the second half of the CCT motif [1]. Toc1 mutants have been identified in this region.

1: Cloning of the Arabidopsis clock gene TOC1, an autoregulatory response regulator homolog. Strayer C, Oyama T, Schultz TF, Raman R, Somers DE, Mas P, Panda S, Kreps JA, Kay SA; Science 2000;289:768-771. PMID:10926537