| Similarity also exists between repeated oligopeptide motifs in Cbr and Cab proteins of photosystems 1 and 2 . ^^^ The relationship between cbr transcript and beta carotene accumulation , the structural similarity between Cbr and Cab proteins , and the presence of potential SRE 1 elements lead us to propose that Cbr represents novel carotenoid binding proteins , whose synthesis might be coordinated with carotenogenic enzymes via an evolutionary conserved regulatory mechanism . . ^^^ |