Translocation of alpha-synuclein expressed in Escherichia coli.

alpha-Synuclein is a major component of Lewy bodies in Parkinson's disease. Although no signal sequence is apparent, alpha-synuclein expressed in Escherichia coli is mostly located in the periplasm. The possibilities that alpha-synuclein translocated into the periplasm across the inner membrane by the SecA or the Tat targeting route identified in bacteria and that alpha-synuclein was released through MscL were excluded. The signal recognition particle-dependent pathway is involved in the translocation of alpha-synuclein. The C-terminal 99-to-140 portion of the alpha-synuclein molecule plays a signal-like role for its translocation into the periplasm, cooperating with the central 61-to-95 section. The N-terminal 1-to-60 region is not required for this translocation.