# Accurate Molecular Decision Making during Protein Biogenesis

> **NIH NIH R35** · CALIFORNIA INSTITUTE OF TECHNOLOGY · 2022 · $970,262

## Abstract

Project Summary: Accurate Molecular Decision Making during Protein Biogenesis
Accurate protein biogenesis is essential for the generation and maintenance of a functional
proteome. Our long term goal is to understand the molecular mechanisms by which diverse
protein biogenesis pathways in the cell accurately select nascent protein substrates and ensure
their correct folding, localization, and maturation. Two major components define our research
program in this grant cycle.
First, we will use a combination of biochemical, biophysical, and in vivo experiments to decipher
the mechanisms by which nascent proteins emerging from the ribosome are selected and
processed by ribosome-associated protein biogenesis factors (RPBs) in the crowded space of
the ribosome tunnel exit. These studies will include a new co-translational membrane protein
targeting pathway mediated by SecA, enzymes mediating N-terminal methionine excision on
nascent proteins in bacteria, and co-translational protein targeting mediated by SRP in the
mammalian system. In addition to studying the biochemical and biophysical mechanisms of the
individual protein biogenesis pathways, we will also elucidate how each of these factors
coordinates with other RPBs in space and time during ongoing translation, and how this
coordination reshapes the efficiency and fidelity of the individual pathways.
Second, we will decipher the mechanisms by which aggregation-prone membrane proteins are
effectively protected and facilely guided to the target membrane during their post-translational
targeting. These studies will use two membrane protein biogenesis pathways as models: (i) an
ATP-independent chaperone cpSRP43, which allows us to decipher, at biophysical resolution,
the molecular mechanisms by which a small chaperone effectively protects multi-pass
membrane protein clients and achieves spatiotemporal regulation of its client interactions in the
absence of ATPase cycles or cochaperones; (ii) the guided-entry of tail-anchored proteins (GET)
pathway, which provides an excellent system to decipher how a multi-component Hsp70-
cochaperone cascade protects, funnels, and triages nascent membrane proteins during their
targeted delivery. Investigation of the GET pathway will also allow us to gain insights into the
design and organizational principles of analogous chaperone networks in the cell.
The proposed experiments will not only generate high resolution understandings of the
individual protein biogenesis pathways, but also establish valuable tools, reagents to explore the
action of other protein biogenesis machineries. Most importantly, this research will generate
important conceptual frameworks to understand how nascent proteins are accurately selected
into their appropriate biogenesis pathways in the crowded cytosolic environment.

## Key facts

- **NIH application ID:** 10372995
- **Project number:** 5R35GM136321-03
- **Recipient organization:** CALIFORNIA INSTITUTE OF TECHNOLOGY
- **Principal Investigator:** Shu-ou Shan
- **Activity code:** R35 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $970,262
- **Award type:** 5
- **Project period:** 2020-04-01 → 2025-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10372995

## Citation

> US National Institutes of Health, RePORTER application 10372995, Accurate Molecular Decision Making during Protein Biogenesis (5R35GM136321-03). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10372995. Licensed CC0.

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