Human Brain βA4 Amyloid Protein Precursor of Alzheimer's Disease: Purification and Partial Characterization

Abstract

Abstract: The major component of the amyloid deposition that characterizes Alzheimer's disease is the 4‐kDa βA4 protein, which is derived from a much larger amyloid protein precursor (APP). A procedure for the complete purification of APP from human brain is described. The same amino terminal sequence of APP was found in two patients with Alzheimer's disease and one control subject. Two major forms of APP were identified in human brain with apparent molecular masses of 100–110 kDa and 120–130 kDa. Soluble and membrane fractions of brain contained nearly equal amounts of APP in both humans and rats. Immunoprecipitation with carboxyl terminus‐directed antibodies indicates that the soluble form..