Ubiquitin (Ub) is a small protein that is composed of 76aa. Ub is found only in eukaryotic organisms and is highly conserved. Ub can exist either in free form or as part of a complex with other proteins. In the latter case, Ub is attached (conjugated) to proteins through a covalent bond between the glycine at the C-terminal end of Ub and the side chains of lysine on the proteins; Ubiquitination. Ub functions to regulate protein turnover in a cell by closely regulating the degradation of specific proteins. Ubiquitin has been immunohistochemically localized to a number of pathological inclusions, including ; Lewy bodies of Parkinson's disease,neurofibrillary of Alzheimer's disease, Pick bodies of Pick's disease.