Unconventional import pathways of the dually localised proteins Thioredoxin 1 and Glutathione peroxidase 3 into the mitochondrial intermembrane space

Dickson-Murray, Eleanor (2021) Unconventional import pathways of the dually localised proteins Thioredoxin 1 and Glutathione peroxidase 3 into the mitochondrial intermembrane space. MSc(R) thesis, University of Glasgow.

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Mitochondria are essential organelles, underpinning a variety of vital cellular functions. However, mitochondrial DNA (mtDNA) encodes for only 13 proteins and therefore the remaining ~1000 proteins in the proteome of Saccharomyces cerevisiae require import into the organelle. All the proteins of the intermembrane space (IMS), a sub-compartment of mitochondria, require import. The main import pathway to the IMS is the mitochondrial import and assembly (MIA) pathway. As well as being the interface between the matrix and the cytosol, the IMS is the site of disulfide bond formation through oxidative folding by the MIA pathway. However, unlike other locations where disulfide bond formation occurs, i.e. the endoplasmic reticulum (ER) and the bacterial periplasm, no reductive pathway has yet been detailed for the IMS. As the major IMS import pathway, the MIA pathway, is subject to redox regulation, it is of interest to investigate proteins that may have a role in balancing the redox environment of the IMS. Having been previously identified as being dually localised between the IMS and the cytosol, the import pathways of the oxidase Glutathione peroxidase 3 (Gpx3) and the reductase Thioredoxin 1 (Trx1) remain unknown. The first part of this thesis focused on investigating the import pathway of Trx1, however as the project developed aims shifted to optimising the import protocol of Trx1. Whilst the import could not be optimised, parameters were identified that can be excluded from having a major role in this import pathway. The second part of this thesis focused on the import pathway of Gpx3 and components that may be involved. The role of the abundant outer membrane proteins Om14 and Om45 were specifically investigated in both a post and co-translational manner with the use of ribosome-stalled Gpx3 RNA. Whilst in a post-translational manner, no effect was observed in the import of Gpx3 into mitochondria containing no Om45, in a cotranslational system an increase in import was observed. This preliminary result suggests that Om45 may play a role in the import of Gpx3 and warrants further investigation in the future. Furthering understanding of the nuances involved in the various protein import pathways into mitochondria will ultimately aid the developments of therapeutics for mitochondrial diseases.

Item Type: Thesis (MSc(R))
Colleges/Schools: College of Medical Veterinary and Life Sciences > Institute of Molecular Cell and Systems Biology
Supervisor's Name: Tokatlidis, Prof. Kostas
Date of Award: 2021
Depositing User: Theses Team
Unique ID: glathesis:2021-82760
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 25 Mar 2022 11:42
Last Modified: 08 Apr 2022 16:42
Thesis DOI: 10.5525/gla.thesis.82760
URI: http://theses.gla.ac.uk/id/eprint/82760

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