MARCKS is the most prominent cellular substrate for protein kinase C. This protein binds calmodulin, actin, and synapsin. MARCKS is a filamentous (F) actin cross-linking protein. Highest levels found in spleen and brain. Intermediate levels seen in thymus, ovary, lung and heart. Very low levels seen in kidney, skeletal muscle and liver. Phosphorylation by PKC displaces MARCKS from the membrane. It also inhibits the F-actin cross-linking activity. Belongs to the MARCKS family.