The localization of Tic20 proteins in Arabidopsis thaliana is not restricted to the inner envelope membrane of chloroplasts |
| |
Authors: | Anu B Machettira Lucia E Gross Maik S Sommer Benjamin L Weis Gisela Englich Joanna Tripp Enrico Schleiff |
| |
Institution: | Department of Biosciences, Molecular Cell Biology of Plants, Johann-Wolfgang-Goethe University Frankfurt, Max-von-Laue Strasse 9, Frankfurt am Main, Germany. |
| |
Abstract: | Tic20 is a central, membrane-embedded component of the precursor protein translocon of the inner envelope of chloroplasts (TIC). In Arabidopsis thaliana, four different isoforms of Tic20 exist. They are annotated as atTic20-I, -II, -IV and -V and form two distinct phylogenetic subfamilies in embryophyta. Consistent with atTic20-I being the only essential isoform for chloroplast development, we show that the protein is exclusively targeted to the chloroplasts inner envelope. The same result is observed for atTic20-II. In contrast, atTic20-V is localized in thylakoids and atTic20-IV dually localizes to chloroplasts and mitochondria. These results together with the previously established expression profiles explain the recently described phenotypes of Tic20 knockout plants and point towards a functional diversification of these proteins within the family. For all Tic20 proteins a 4-helix topology is proposed irrespective of the targeted membrane, which in part could be confirmed in vivo by application of a self-assembling GFP-based topology approach. By the same approach we show that the inner envelope localized Tic20 proteins expose their C-termini to the chloroplast stroma. This localization would be consistent with the positive inside rule considering a stromal translocation intermediate as discussed. |
| |
Keywords: | |
本文献已被 PubMed SpringerLink 等数据库收录! |
|