Nerve growth factor (NGF) protomer. NGF is a member of an expanding family of neurotrophic factors that control the development and survival of certain neuronal populations both in the peripheral and in the central nervous systems. NGF is a dimeric molecule, with 118 amino acids per protomer.

  Transparent view of NGF protomer.

  Observe the three antiparallel pairs of beta-strands, together forming a flat surface. Two subunits associate through this surface, thus burying a large number of residues. Four loop regions, which contain many of the variable residues observed between different NGF-related molecules, may determine the different receptor specificities.

  Spacefilled model.