TARGETING OF PROTEINS TO THE THYLAKOIDS BY BIPARTITE PRESEQUENCES - CFOLL IS IMPORTED BY A NOVEL, 3RD PATHWAY

被引:108
作者
MICHL, D
ROBINSON, C
SHACKLETON, JB
HERRMANN, RG
KLOSGEN, RB
机构
[1] UNIV MUNICH,INST BOT,MENZINGER STR 67,D-80638 MUNICH,GERMANY
[2] UNIV WARWICK,DEPT BIOL SCI,COVENTRY CV4 7AL,W MIDLANDS,ENGLAND
关键词
ATP SYNTHASE; CHLOROPLAST; PROTEIN TRANSPORT; THYLAKOID BIOGENESIS;
D O I
10.1002/j.1460-2075.1994.tb06383.x
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The CFoII subunit of the ATP synthase is an integral component of the thylakoid membrane which is synthesized in the cytosol with a bipartite, lumen-targeting presequence similar in structural terms to those of imported lumenal proteins such as plastocyanin. This presequence is shown to possess a terminal cleavage site for the thylakoidal processing peptidase, but no intermediate site for the stromal processing peptidase. The integration of CFoII into the thylakoid membrane of Pisum sativum has been analysed using in vitro assays for the import of proteins into intact chloroplasts or isolated thylakoids. Efficient integration into thylakoids is observed in the light and dark, and the integration process does not require the presence of either stromal extracts or nucleoside triphosphates. The uncoupler nigericin inhibits integration only very slightly, indicating that the thylakoidal delta pH does not play a significant role in the integration mechanism. In each of these respects, the requirements for CFoII integration differ notably from those determined for integration of the fight-harvesting chlorophyll-binding protein of photosystem II. The integration mechanism also differs significantly from the two mechanisms involved in the translocation of lumenal proteins across the thylakoid membrane, since one of these processes requires the presence of stromal protein factors and ATP, and the other mechanism is dependent on the thylakoidal delta pH. This conclusion is reinforced by the finding that saturation of the translocation system for the precursor to the lumenal 23 kDa oxygen-evolving complex protein does not affect integration of CFoII into thylakoids. Among proteins which are targeted into thylakoids by means of bipartite presequences, CFoII is therefore imported by a novel, third pathway.
引用
收藏
页码:1310 / 1317
页数:8
相关论文
共 34 条