title: Tat transport of a Sec passenger leads to both completely translocated as well as membrane-arrested passenger proteins.
abstract: We have studied the membrane transport of the chimeric precursor protein 16/33, which is composed of the Tat(1)-specific transport signal of OEC16 and the Sec passenger protein OEC33, both subunits of the oxygen-evolving system associated with photosystem II. Protein transport experiments performed with isolated pea thylakoids show that the 16/33 chimera is transported in a strictly Tat-dependent manner into the thylakoid vesicles yielding mature OEC33 (mOEC33) in two different topologies. One fraction accumulates in the thylakoid lumen and is thus resistant to externally added protease. A second fraction is arrested during transport in an N-in/C-out topology within the membrane. Chase experiments demonstrate that this membrane-arrested mOEC33 moiety does not represent a translocation intermediate but instead an alternative end product of the transport process. Transport arrest of mOEC33, which is embedded in the membrane with a mildly hydrophobic protein segment, requires more than 26 additional and predominantly hydrophilic residues C-terminal of the membrane-embedded segment. Furthermore, it is stimulated by mutations which potentially affect the conformation of mOEC33 suggesting that at least partial folding of the passenger protein is required for complete membrane translocation.
authors: Institute of Biology-Plant Physiology, Martin-Luther-University Halle-Wittenberg, Weinbergweg 10, 06120 Halle/Saale, Germany.
authors: Julia
authors: J
authors: Dittmar
authors: Institute of Biology-Plant Physiology, Martin-Luther-University Halle-Wittenberg, Weinbergweg 10, 06120 Halle/Saale, Germany.
authors: René
authors: R
authors: Schlesier
authors: Institute of Biology-Plant Physiology, Martin-Luther-University Halle-Wittenberg, Weinbergweg 10, 06120 Halle/Saale, Germany. Electronic address: klosgen@pflanzenphys.uni-halle.de.
authors: Ralf Bernd
authors: RB
authors: Klösgen
mesh_terms: D000595:Amino Acid Sequence; D057927:Hydrophobic and Hydrophilic Interactions; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D018532:Pisum sativum / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D010447:Peptide Hydrolases / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism*; D021381:Protein Transport; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D020524:Thylakoids / Q000378:metabolism
chemical_list: D026901:Membrane Transport Proteins; D050505:Mutant Proteins; D010446:Peptide Fragments; D010940:Plant Proteins; D011994:Recombinant Proteins; D010447:Peptide Hydrolases
keywords: 16 (23,33) kDa subunit of the oxygen-evolving system associated with photosystem II; Membrane arrest; OEC16 (23,33); PAGE; Protein transport; Sec; Stop-transfer; TPP; Tat; Tat pathway; Thylakoid membrane; Ti-1(-2); Twin-arginine translocation; mOEC33; mature OEC33; polyacrylamide gel electrophoresis; preOEC33; precursor OEC33; secretory; thylakoidal processing peptidase; translocation intermediate-1(-2); twin-arginine translocation