MARCKS, a major protein kinase C substrate assumes non-helical conformations both in solution and in complex with Ca²⁺-calmodulin

MARCKS, a major cellular substrate for protein kinase C, plays important roles in various cellular functions and its functions are regulated by calmodulin. We have studied the conformational properties of recombinant human MARCKS in solution and in complex with calmodulin. Circular dichroism (CD) spectra showed a high content of random coil in physiological solution. When MARCKS or MARCKS-derived calmodulin-binding peptide was complexed with Ca²⁺-calmodulin, little changes was observed in the CD spectra, suggesting that MARCKS binds with calmodulin in a non-helical conformation, which is unique among the calmodulin in a non-helical conformation, which is unique among the calmodulin-binding proteins.