# Towards an Atomistic Understanding of Mitochondrial Protein Biogenesis

> **NIH NIH R35** · UNIVERSITY OF CALIFORNIA, SAN DIEGO · 2020 · $356,947

## Abstract

PROJECT SUMMARY
Maintaining mitochondrial integrity is necessary for normal eukaryotic physiology and, not surprisingly,
mitochondrial dysfunction is a pathological hallmark of diseases and has been implicated as a primary risk factor
for many cancers and neurodegenerative disorders. Critical to mitochondrial function is its dual-membrane
architecture which provides appropriate microenvironments that facilitate specific metabolic functions – such as
oxidative phosphorylation – and allow for otherwise incompatible processes to occur simultaneously inside the
cell. Traditionally, research on mitochondria have focused on bioenergetics, but recent studies have begun to
shed light on the intricacies and complexities of the mitochondrial proteome and the biogenesis machineries.
This is particularly important as >99% of the mitochondrial proteome (~1500 proteins in humans) are encoded
by nuclear genes and synthesized by cytosolic ribosomes as precursor proteins (preproteins). These preproteins
contain endogenous signals that target them to mitochondria, where they are subsequently translocated across
the outer membrane, sorted, compartmentalized, and properly folded by three main protein import machineries:
the translocase of the outer mitochondrial membrane (TOM) complex, the mitochondrial translocase of the inner
membrane (TIM)-23 complex (TIM23), and the TIM22 complex. These protein import complexes are required for
the biogenesis of nearly all mitochondrial proteins and dysregulation poses a significant challenge to maintaining
normal mitochondrial physiology. However, a dearth of structural information has precluded a molecular
understanding of these processes and the mechanisms by which they perform their critical functions.
 Under this award, I will develop groundbreaking three-dimensional (3D) electron cryomicroscopy
(cryoEM) technologies to pioneer studies of these critically important mitochondrial protein import complexes,
providing critical insights into their function and their roles in the disease state. I will utilize targeted biochemical
approaches to isolate the TOM, TIM23, and TIM22 complexes from natural sources for high-resolution cryoEM
studies. I will then develop novel EM sample preparation, data collection and data processing strategies to yield
a suite of high-resolution structures of each of these import machines during active preprotein import. I will then
quantify the degree of local and global dynamics within these states through novel atomic modeling strategies
as a means to define the conformational landscape. I will then establish in vitro functional assays to test key
molecular steps during these processes. Lastly, I will then develop correlated light microscopy and high-
resolution electron cryotomography (cryoET) methodologies to determine structure of these import complexes
in their native membranes. Through these combined efforts, I will answer fundamental questions pertaining to
the overall 3D architecture of these ...

## Key facts

- **NIH application ID:** 10029370
- **Project number:** 1R35GM138206-01
- **Recipient organization:** UNIVERSITY OF CALIFORNIA, SAN DIEGO
- **Principal Investigator:** Mark Anthony Herzik
- **Activity code:** R35 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $356,947
- **Award type:** 1
- **Project period:** 2020-07-01 → 2025-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10029370

## Citation

> US National Institutes of Health, RePORTER application 10029370, Towards an Atomistic Understanding of Mitochondrial Protein Biogenesis (1R35GM138206-01). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10029370. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*