GAP-43 is associated with nerve growth and is a major component of the motile "growth cones" of elongating axons. Human GAP-43 is a 238 amino acid protein of predicted molecular weight 24.8 kDa. GAP-43 binds calmodulin with a greater affinity in the absence of Ca(2+) than in its presence. Its phosphorylation by a protein Kinase C is correlated with certain forms of synaptic plasticity.