CLOCK and BMAL1 are transcriptional factors of the circadian genes in mammals. These proteins form a dimer and bind to E-box, a DNA sequence which usually lies upstream of a gene in a promoter region. E-BOX activation turn on hundreds of effector genes whose products control a wide variety of metabolic functions (e.g., cellular respiration,glycolisys, lipid metabolism, etc)
The structure of the CLOCK -BMAL1 dimer (PDB entry 4h10 ) which was published by Wang, Z., Wu, Y., Li, L., and Su, X.D., in 2012 in a paper entitled “Intermolecular recognition revealed by the complex structure of human CLOCK-BMAL1 basic helix-loop-helix domains with E-box DNA.” (abstract).
Unfortunately, there is no protein structure for this complex.