The carboxyl terminus of nerve growth factor is required for biological activity.

A series of mouse nerve growth factor (NGF) deletion mutants have been constructed using in vitro mutagenesis to define domains of the protein essential for its activity. Deletions of the amino or carboxyl termini of mature NGF or of an internal domain, which normally produces a surface-exposed reverse turn, have been analyzed. Mutants with deletions in the amino terminus or in the reverse turn retain significant biological activity, whereas, in contrast, a mutant NGF lacking the seven most carboxyl-terminal amino acids is appropriately synthesized but shows no measurable biological activity. These results suggests that the flexible carboxyl tail of NGF, and perhaps other neurotrophins, plays a crucial role in mediating receptor recognition and/or ligand binding.