# Determining the mechanism of mitochondrial outer membrane fusion

> **NIH NIH R01** · UNIVERSITY OF WASHINGTON · 2020 · $291,556

## Abstract

Project Summary
Mitochondria are required for a myriad of cellular functions. The mitochondrial network in cells is established
and maintained by the coordinate activities of movement, fusion and division. Mitochondrial fusion in
particular is beneficial as it increases cellular energy and protects against cell death. The molecular machines
that mediate mitochondrial outer and inner membrane fusion are members of the dynamin superfamily. As
such, they are large self-assembling GTPases that harness the energy from nucleotide hydrolysis to remodel
membranes. How these proteins couple self-assembly and the catalytic cycle to membrane tethering and lipid
mixing is not known. The focus of this work is to examine the molecular mechanism of mitochondrial outer
membrane fusion. Although Mitofusin1 (Mfn1) and Mitofusin2 (Mfn2) are both required for mitochondrial outer
membrane fusion, they are functionally distinct. We discovered that mitochondrial fusion is most efficient
when Mfn1 and Mfn2 are on opposite membranes. This suggests that they have unique molecular
characteristics. To address this, we will compare and contrast Mfn1 and Mfn2 throughout our analyses and
determine their unique biochemical properties. Our evaluation of the GTPase domain will reveal the
mechanism of nucleotide binding, hydrolysis and release. We will reconstitute Mitofusin-dependent
membrane tethering. This will allow us to determine the role of the catalytic cycle in membrane tethering and
the role of lipid composition on Mitofusin tethering activity. Using disease associated missense mutations, we
will identify unique features of the GTPase domain. We will identify the molecular determinants of Mitofusin
complex assembly. We will combine cellular studies with powerful biochemical analyses, including
reconstitution of lipid and content mixing with proteoliposomes. These studies will provide new insight into the
unique mechanism of mitochondrial outer membrane fusion.

## Key facts

- **NIH application ID:** 9857029
- **Project number:** 5R01GM118509-04
- **Recipient organization:** UNIVERSITY OF WASHINGTON
- **Principal Investigator:** Suzanne C Hoppins
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $291,556
- **Award type:** 5
- **Project period:** 2017-02-01 → 2022-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9857029

## Citation

> US National Institutes of Health, RePORTER application 9857029, Determining the mechanism of mitochondrial outer membrane fusion (5R01GM118509-04). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9857029. Licensed CC0.

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