Ubiquitin is a component of polypeptides purified from corpora amylacea of aged human brain.

Corpora amylacea (CA) are one of the conspicuous features of brain tissue in normal aging and neurodegenerative diseases. Quantitative protein determination of purified CA revealed a protein content of about 4% of total weight. Qualitative protein analysis revealed a broad range of polypeptides, with four being more abundant. High performance liquid chromatography (HPLC) fractionation of this protein material showed four peaks which are related to the four major polypeptides with molecular weights of 24 KD, 42 KD, 94 KD, and 133 KD. Amino acid content analysis of the 24 KD, 42 KD and 94 KD polypeptides indicated that distinct protein species are involved. N-terminal amino acid sequence analysis of the 24 KD and 42 KD polypeptides revealed in both cases homology with the N-terminal sequence of human ubiquitin.