Investigation of Clock Protein Interactions by Surface Plasmon Resonance

Biological clock in humans can be defined as 24 hour rhythm in behavior and sleep-wake cycle. This rhythm is regulated by four main proteins (BMAL1, CLOCK, PERIODS, and CRYPTOCHROMES).  CLOCK and BMAL1 proteins form dimers and bind to the E-box motifs on the promoter region to enhance the gene transcription. PER2 and CRY accumulates within the cytosol and transfer into the nucleus where they interact with CLOCK and BMAL1 and suppress the gene expression driven by BMAL1 and CLOCK. However the exact mechanism could not be identified yet in eukaryotes in procaryotes. In this study, we investigate the clock mechanism protein interactions using surface plasmon resonance (SPR). Kinetic parameters for the interactions are determined from real time interactions for a solid insight into the interactions of biological clock mechanism. The interaction affinity results support the previous biochemical assays, and is significant to quantify binding constants between these proteins for the first time in the literature. The study also provides a better understanding of the role and the mechanism of biological clock, where information about the interaction of these proteins among themselves will be useful for the development of drugs rationally against the clock-related diseases.