MARCKS proteins (myristoylated alanine-rich C-kinase substrate) play important roles in cell mobility, secretion, transmembrane transport, and regulation of the cell cycle.

They are acidic proteins with high proportions of alanine, glycine, proline, and glutamic acid. They are membrane-bound through a lipid anchor at the N-terminus. They are regulated by Ca2+/calmodulin and protein kinase C. In their phosphorylated form, they bind to actin filaments, causing them to crosslink.