Chloroplast Import of an Intermembrane Space Protein is Facilitated by Translocon Components Toc75 and Tic236

Overview

Journal Plant Direct

Specialty Biology

Date 2021 Nov 12

PMID 34765862

Citations 5

Authors

Meng-Rong Chuang

Lih-Jen Chen

Hsou-Min Li

Affiliations

Soon will be listed here.

Abstract

Chloroplasts are divided into six subcompartments: the outer membrane, intermembrane space, and inner membrane of the envelope, the stroma, the thylakoid membrane, and the thylakoid lumen. Compared with our knowledge of protein import into other subcompartments, extremely little is known about how proteins are imported into the intermembrane space of the envelope. Tic22 was one of the first proteins identified as localizing to the intermembrane space and the only one for which import has been analyzed in some detail. However, conflicting results have been obtained concerning whether the general translocon is used to import Tic22 into the intermembrane space. Taking advantage of available translocon component mutants, we reanalyzed import of Tic22. We reveal reduced in vitro import of Tic22 preprotein (prTic22) into chloroplasts isolated from the Arabidopsis and mutants, which are functional knockdown mutants of the outer-membrane channel Toc75 and the intermembrane space linker Tic236, respectively. Import competition experiments also showed that prTic22 import was reduced by excess amounts of a stroma-targeted preprotein. Our results indicate that prTic22 uses at least part of the general translocon for import into the intermembrane space.

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Chloroplast import of an intermembrane space protein is facilitated by translocon components Toc75 and Tic236.

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