The yeast split-ubiquitin system to study chloroplast membrane protein interactions.
Each photosynthetic complex within the thylakoid membrane consists of several different subunits. During formation of these complexes, numerous regulatory factors are required for the coordinated transport and assembly of the subunits. Interactions between transport/assembly factors and their specific polypeptides occur in a membraneous environment and are usually transient and short-lived. Thus, a detailed analysis of the underlying molecular mechanisms by biochemical techniques is often difficult to perform. Here, we report on the suitability of a genetic system, i.e. the yeast split-ubiquitin system, to investigate protein-protein interactions of thylakoid membrane proteins. The data confirm the previously established binding of the cpSec-translocase subunits, cpSecY and cpSecE, and the interaction of the cpSec-translocase from Arabidopsis thaliana with Alb3, a factor required for the insertion of the light-harvesting chlorophyll-binding proteins into the thylakoid membrane. In addition, the proposed interaction between D1, the reaction center protein of photosystem II and the soluble periplasmic PratA factor from Synechocystis sp. PCC 6803 was verified. A more comprehensive analysis of Alb3-interacting proteins revealed that Alb3 is able to form dimers or oligomers. Interestingly, Alb3 was also shown to bind to the PSII proteins D1, D2 and CP43, to the PSI reaction center protein PSI-A and the ATP synthase subunit CF(0)III, suggesting an important role of Alb3 in the assembly of photosynthetic thylakoid membrane complexes.
Lehrstuhl für Allgemeine und Molekulare Botanik, Ruhr-Universität Bochum, 44780 Bochum, Germany.
Jan Christoph
JC
Pasch
Jörg
J
Nickelsen
Danja
D
Schünemann
D017360:Arabidopsis / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000378:metabolism; D060365:Chloroplast Proteins; D002736:Chloroplasts / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D033903:Periplasmic Proteins / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000378:metabolism; D000069816:SEC Translocation Channels; D046939:Synechocystis / Q000378:metabolism; D020524:Thylakoids; D020798:Two-Hybrid System Techniques; D025801:Ubiquitin / Q000378:metabolism*
C106404:ALBINO 3 protein, Arabidopsis; D029681:Arabidopsis Proteins; D060365:Chloroplast Proteins; D008565:Membrane Proteins; D033903:Periplasmic Proteins; D045332:Photosystem II Protein Complex; C000613370:SCY1 protein, Arabidopsis; D000069816:SEC Translocation Channels; D025801:Ubiquitin; C422369:photosystem II, psbA subunit