Although the structural basis for how BMAL1/CLOCK interact with the E-box is unknown, recent research has shown that the bHLH protein domains of BMAL1/CLOCK are highly similar to other bHLH containing proteins, e.g. Myc/Max, which have been crystallized with E-boxes.
The relationship between BMAL1/CLOCK and the E-box is not yet fully comprehended. Nevertheless, recent research has highlighted that the bHLH protein domains of BMAL1/CLOCK exhibit considerable homology to those found in Myc/Max proteins, which have been structurally characterized in complex with E-boxes.