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Protein translocation at the endoplasmic reticulum membrane in Arabidopsis thaliana
Protein translocation at the endoplasmic reticulum membrane in Arabidopsis thaliana
Protein translocation into or across the endoplasmic reticulum (ER) membrane via the Sec translocon occurs either co-translationally or in a post-translational manner. Despite involved components being well investigated in yeast and humans, there is only scarce knowledge regarding the Arabidopsis Sec translocon. It is composed of the central Sec61 complex, the J-domain containing AtERdj2A/B and the luminal AtBiP. It additionally involves the recently described chaperone docking protein AtTPR7, the yet uncharacterised AtSec62 as well as cytosolic chaperones for post-translational translocation. In this study, an atsec62 T-DNA insertion line was characterised revealing the importance of AtSec62 for vegetative and generative growth resulting in an altered root morphology, impaired growth and reduced male fertility in atsec62 probably due to the involvement of AtSec62 in protein translocation and subsequent secretion. atsec62 displayed an increased susceptibility towards high-temperature and ER stress, indicating that it might be involved in ER stress recovery similar to human Sec62. In contrast to its yeast and human homologues, AtSec62 was shown to have an additional third transmembrane domain with its luminal exposed C-terminus being crucial for proper AtSec62 function in Arabidopsis. Potential AtSec62 interacting or associating proteins were identified, including other Sec translocon components like AtTPR7 and subunits of the Sec61 complex, the GET-pathway proteins AtGET1 and AtGET3a and other proteins like AtATG8e, AtCNX1 and the tail-anchored protein AtSYP123. Moreover, the interaction of AtTPR7 with putative candidates for post-translational translocation like AtPYK10 and AtGLL23 was confirmed by in vitro pull-down assays. The investigation of AtSec62 topology as well as AtSec62 and AtTPR7 interacting proteins provides further insight into the composition of the Arabidopsis Sec post-translocon and reveals potential translocation substrates. However, the exact function of respective components and the general mechanism of translocation still remain unknown and should be addressed in future studies.
ER, protein translocation, Arabidopsis thaliana, AtSec62, AtTPR7
Mitterreiter, Melanie Jasmine
2020
English
Universitätsbibliothek der Ludwig-Maximilians-Universität München
Mitterreiter, Melanie Jasmine (2020): Protein translocation at the endoplasmic reticulum membrane in Arabidopsis thaliana. Dissertation, LMU München: Faculty of Biology
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Abstract

Protein translocation into or across the endoplasmic reticulum (ER) membrane via the Sec translocon occurs either co-translationally or in a post-translational manner. Despite involved components being well investigated in yeast and humans, there is only scarce knowledge regarding the Arabidopsis Sec translocon. It is composed of the central Sec61 complex, the J-domain containing AtERdj2A/B and the luminal AtBiP. It additionally involves the recently described chaperone docking protein AtTPR7, the yet uncharacterised AtSec62 as well as cytosolic chaperones for post-translational translocation. In this study, an atsec62 T-DNA insertion line was characterised revealing the importance of AtSec62 for vegetative and generative growth resulting in an altered root morphology, impaired growth and reduced male fertility in atsec62 probably due to the involvement of AtSec62 in protein translocation and subsequent secretion. atsec62 displayed an increased susceptibility towards high-temperature and ER stress, indicating that it might be involved in ER stress recovery similar to human Sec62. In contrast to its yeast and human homologues, AtSec62 was shown to have an additional third transmembrane domain with its luminal exposed C-terminus being crucial for proper AtSec62 function in Arabidopsis. Potential AtSec62 interacting or associating proteins were identified, including other Sec translocon components like AtTPR7 and subunits of the Sec61 complex, the GET-pathway proteins AtGET1 and AtGET3a and other proteins like AtATG8e, AtCNX1 and the tail-anchored protein AtSYP123. Moreover, the interaction of AtTPR7 with putative candidates for post-translational translocation like AtPYK10 and AtGLL23 was confirmed by in vitro pull-down assays. The investigation of AtSec62 topology as well as AtSec62 and AtTPR7 interacting proteins provides further insight into the composition of the Arabidopsis Sec post-translocon and reveals potential translocation substrates. However, the exact function of respective components and the general mechanism of translocation still remain unknown and should be addressed in future studies.