This N-terminal domain of APP, amyloid precursor protein, is the heparin-binding domain of the protein. this region is also responsible for stimulation of neurite outgrowth. The structure reveals both a highly charged basic surface that may interact with glycosaminoglycans in the brain and an abutting hydrophobic surface that is proposed to play an important functional role such as in dimerisation or ligand-binding. Structural similarities with cysteine-rich growth factors, taken together with its known growth-promoting properties, suggest the APP N-terminal domain could function as a growth factor in vivo [1].

1: Crystal structure of the N-terminal, growth factor-like domain of Alzheimer amyloid precursor protein. Rossjohn J, Cappai R, Feil SC, Henry A, McKinstry WJ, Galatis D, Hesse L, Multhaup G, Beyreuther K, Masters CL, Parker MW; Nat Struct Biol. 1999;6:327-331. PMID:10201399