Two distinct translocation intermediates can be distinguished during protein transport by the TAT (Delta ph) pathway across the thylakoid membrane

During thylakoid transport of the chimeric precursor protein 16/23 which ta kes place by the twin arginine translocation (TAT) (Delta ph)-dependent pat hway, two distinct translocation intermediates can be identified which repr esent successive steps in the translocation process, Both intermediates are partially inserted into the thylakoid membrane and can be distinguished by specific degradation fragments occurring after thermolysin treatment of th e thylakoids, While the formation of the early translocation intermediate d oes not depend on a functional TAT translocation machinery, the appearance of the late intermediate is strictly coupled to the Delta ph-dependent tran sport of the 16/23 chimera. Accordingly, this translocation intermediate is found associated with two distinct complexes in the thylakoid membrane hav ing apparent molecular masses of approximately 560 and 620 kDa, respectivel y. (C) 1999 Federation of European Biochemical Societies.