The tricarboxylic acid cycle enzyme aconitase in yeast is a single translation product, which is dual targeted and distributed between the mitochondria and the cytosol by a unique mechanism involving reverse translocation. There is limited understanding regarding the precise mechanism of reverse translocation across the mitochondrial membranes. Here, we examined the contribution of the mature part of aconitase to its dual targeting. We created a set of aconitase mutants harboring two kinds of alterations: (1) point mutations or very small deletions in conserved sites and (2) systematic large deletions. These mutants were screened for their localization by a α-complementation assay, which revealed that the aconitase fourth domain that is at the C-terminus (amino acids 517-778) is required for aconitase distribution. Moreover, fusion of this C-terminal domain to mitochondria- targeted passenger proteins such as dihydrofolate reductase and orotidine-5′-phosphate decarboxylase, conferred dual localization on them. These results indicate that the aconitase C-terminal domain is both necessary and sufficient for dual targeting, thereby functioning as an "independent signal". In addition, the same C-terminal domain was shown to be necessary for aconitase efficient posttranslational import into mitochondria.
Bibliographical noteFunding Information:
We thank Efrat Burak and Tanya Shechter for their dedicated assistance. This study was supported by grants from the Israel Science Foundation (ISF), The Niedersachsen-Israeli Research Cooperation, The USA – Israel Binational Science Foundation (BSF) and the CREATE project of the National Research Foundation of Singapore. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
- Saccharomyces cerevisiae
- dual targeting
- reverse translocation