Myristoylated alanine-rich protein kinase C substrate (MARCKS), also designated 80K or 80K-L, has been identified as a major cellular substrate for protein kinase C. Human MARCKS is a 332 amino acid protein with a calculated molecular weight of 31.534 kDa; however, it has been shown to run at 80-87 kDa on Western blot. The plasma membrane bound protein dissociates from the membrane upon phosphorylation by various PKC isoforms. In NIH/3T3 fibroblasts, PKC alpha and PKC E, but not PKC delta, are responsible for MARCKS phosphorylation. MARCKS has been found to bind calmodulin, Actin and Synapsin and is a filamentous (F) Actin crosslinking protein.