# Biogenesis of alpha-helical mitochondrial outer membrane proteins in higher eukaryotes

> **NIH NIH K99** · CALIFORNIA INSTITUTE OF TECHNOLOGY · 2024 · $125,000

## Abstract

Project Summary/Abstract
Mitochondria are essential organelles of endosymbiotic origin which have evolved to play critical roles in
eukaryotic physiology. Mitochondrial activity is dependent on proteins embedded in the outer mitochondrial
membrane (OMM), which mediate mitochondrial-cytoplasmic communication, and critical aspects of cellular
function such as apoptosis and the innate immune response. a-helical proteins are an important subset of
OMM proteins. However, how they get inserted into the lipid bilayer of the OMM in mammalian cells has until
recently been unclear.
 Work by myself, in collaboration with Rebecca Voorhees and Jonathan Weissman’s labs, has identified
the OMM resident protein MTCH2, a defining member of a novel family of insertases, as both necessary and
sufficient for the insertion of a-helical proteins into the OMM. MTCH2 is a diverged member of the solute
carrier family 25 (SLC25), and has evolved to exploit the canonical transporter fold for insertion. Bioinformatic
analysis reveals that MTCH2 has a homolog in peroxisomes, and orthologs across holozoa, suggesting a
common mechanism for a-helical protein insertion across membranes and eukaryotes.
 Building on this finding, this proposal aims to develop a comprehensive understanding of how a-helical
proteins are correctly targeted to the OMM and inserted into the lipid bilayer across eukaryotes. This work will
address a fundamental question in cell biology, as the OMM proteome has evolved to support increasingly
more complex functions in higher eukaryotes. a-helical proteins are defined by the presence of one or more
transmembrane domains (TAs), though their TMs can vary significantly in number and a range of biophysical
characteristics such as hydrophobicity. This proposal aims to first develop a deeper understanding of MTCH2
function. First, in vivo and biochemical techniques will be combined to map the route a substrate TM takes
through MTCH2 into the lipid bilayer, directly testing whether MTCH2’s conserved hydrophilic groove has a
direct role in this process. Second, this work will establish whether structural homologs of MTCH2 have
retained their insertase ability across eukaryotes.
 The biochemical skills and knowledge acquired by defining the molecular basis for MTCH2 will be
combined with systematic functional genomics to establish how a-helical proteins get targeted to the OMM,
and whether other factors besides MTCH2 are required to support the biogenesis of this diverse class.
Cumulatively, this proposal will provide important insights into the mechanisms that have evolved to support
eukaryotic life. Further, intimate knowledge of the machinery that governs a-helical OMM protein insertion will
be critical for developing new treatments associated with outer mitochondrial membrane protein dysregulation,
including neurodegenerative diseases such as Parkinson’s and Alzheimer’s.

## Key facts

- **NIH application ID:** 10891727
- **Project number:** 5K99GM151478-02
- **Recipient organization:** CALIFORNIA INSTITUTE OF TECHNOLOGY
- **Principal Investigator:** ALINA-IOANA GUNA
- **Activity code:** K99 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $125,000
- **Award type:** 5
- **Project period:** 2023-08-01 → 2025-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10891727

## Citation

> US National Institutes of Health, RePORTER application 10891727, Biogenesis of alpha-helical mitochondrial outer membrane proteins in higher eukaryotes (5K99GM151478-02). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10891727. Licensed CC0.

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