All synucleins have in common a highly conserved alpha-helical lipid-binding motif with similarity to the class-A2 lipid-binding domains of the exchangeable apolipoproteins. Synuclein family members are not found outside vertebrates, although they have some conserved structural similarity with plant 'late-embryo-abundant' proteins.[1]
Normal cellular functions have not been determined for any of the synuclein proteins. Some data suggest a role in the regulation of membrane stability and/or turnover.[4] Mutations in alpha-synuclein are associated with early-onset familial Parkinson's disease and the protein aggregates abnormally in Parkinson's disease, Lewy body disease, and other neurodegenerative diseases.[5][6] The gamma-synuclein protein's expression in breast tumors is a marker for tumor progression.[7][8]