Abstract
Abstract Calmodulin (CaM) is the major calcium sensor protein in eukaryotic cells. It has been known to interact with more than one hundred substrates and control the physiological events including development, muscle contraction, and differentiation. Myristoylated alanin-rich C kinase substrate (MARCKS) is the substrate of CaM, and is a membrane associated protein. It plays important roles in various cellular functions including postnatal survival, cellular migration, and brain development. The effetor domain (ED) is its binding domain to CaM and is also the major functional region to interact with many substrates. The crystal structure of MARCKS effector domain-CaM complex, and the affinity between MARCKS effector domain and CaM have been reported. The CaM shows high affinity to the MARCKS effector domain. In this study, we apply fluorescence and absorption spectroscopy to investigate the interaction of the two proteins. The binding process was monitored by the change of fluorescence and absorption spectra in the titration experiment. The dissociation constant Kd was determined to be about 357 nM. In this experiment, the FRET between donor and acceptor was not observed. We suggested that this is due to the long distance between donor and acceptor. This is our pilot experiment for the future fluorescence correlation spectroscopy studies.