The molecular basis for ER tubule formation

Thesis

Integral membrane proteins of the DP1 and reticulon families are responsible for maintaining the high membrane curvature required for both smooth ER tubules and the edges of ER sheets. Mutations in these proteins lead to motor neurone diseases such as hereditary spastic paraplegia. Reticulon/DP1 proteins contain Reticulon Homology Domains (RHD) that have unusually long (≈30 aa) hydrophobic segments and are proposed to adopt intramembrane helical hairpins that stabilise membrane curvature. I have uncovered the secondary structure and dynamics of the DP1 protein Yop1p and identified a C-terminal conserved amphipathic helix that on its own interacts strongly with negatively charged membranes and is necessary for membrane tubule formation. Analyses of DP1 and reticulon family members indicate that most, if not all, contain C-terminal sequences capable of forming amphipathic helices. Together, these results indicate that amphipathic helices play a previously unrecognised role in RHD membrane curvature stabilisation. This work paves the way towards full structure determination of Yop1p by solution state NMR and marks the first high structural resolution study on an RHD protein.

Authors: Brady, JP

• Publication date: 2015
• DOI: 10.5287/ora-5zynddp4e
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: nuclear magnetic resonance; tubular ER; reticulon; amphipathic helix; NMR; membrane proteins; DP1; endoplasmic reticulum; Yop1p
• Subjects: Molecular biophysics (biochemistry)