Preprotein recognition by the Toc complex.

Preprotein recognition and translocation by the Toc complex

The targeting of the atToc159 preprotein receptor to the chloroplast outer membrane is mediated by its GTPase domain and is regulated by GTP

The multimeric translocon at the outer envelope membrane of chloroplasts (Toc) initiates the recognition and import of nuclear-encoded preproteins into chloroplasts. Two Toc GTPases, Toc159 and Toc33/34, mediate preprotein recognition and regulate preprotein translocation. Although these two proteins account for the requirement of GTP hydrolysis for import, the functional significance of GTP bi...

Characterization of the preprotein translocon at the outer envelope membrane of chloroplasts by blue native PAGE.

The preprotein translocon at the outer envelope membrane of chloroplasts (Toc) mediates the recognition and import of nuclear-encoded preproteins into chloroplasts. Two receptor components, Toc159 and Toc34, and the channel Toc75 form the Toc complex. In this study, we have analyzed the molecular architecture and organization of the Toc complex by blue native PAGE (BN-PAGE), which is a high-res...

Toc receptor dimerization participates in the initiation of membrane translocation during protein import into chloroplasts.

The post-translational import of nucleus-encoded preproteins into chloroplasts occurs through multimeric translocons in the outer (Toc) and inner (Tic) membranes. The high fidelity of the protein import process is maintained by specific recognition of the transit peptide of preproteins by the coordinate activities of two homologous GTPase Toc receptors, Toc34 and Toc159. Structural and biochemi...

A toc159 import receptor mutant, defective in hydrolysis of GTP, supports preprotein import into chloroplasts.

The heterotrimeric Toc core complex of the chloroplast protein import apparatus contains two GTPases, Toc159 and Toc34, together with the protein-conducting channel Toc75. Toc159 and Toc34 are exposed at the chloroplast surface and function in preprotein recognition. Together, they have been shown to facilitate the import of photosynthetic proteins into chloroplasts in Arabidopsis. Consequently...