# Membrane Protein Folding and Assembly

> **NIH NIH R35** · UNIVERSITY OF CALIFORNIA-IRVINE · 2021 · $472,000

## Abstract

Save date: 15 Jan 2020, 22:40
ABSTRACT
Membrane Protein Folding and Assembly
 Many human diseases, such as cystic fibrosis, result from misfolding of membrane proteins
(MPs) during their synthesis and targeting. It is therefore important to understand the principles
and mechanism of MP folding and assembly. A largely unexplored part of the problem is to
understand folding in the context of the cellular milieu. Toward that goal, we are studying the
targeting, secretion, and insertion of membrane proteins along the so-called SecA post-
translational pathway of living Escherichia coli. We have shown that the SecA motor ATPase,
a significant drug target, can insert single-span membrane proteins (S-SMPs) across the E. coli
inner membrane. This simplified in vivo model system eliminates the many unanswered
questions about the folding of multi-span MPs along the signal recognition particle (SRP)
pathway, because we gain direct access to the translocon-bilayer partitioning process.
 We have engineered two different chimeric protein families for probing systematically S-
SMP stability using TM segments of the form GGPG-H-GPGG (used in an earlier study to
determine a biological hydrophobicity scale using a cell-free eukaryotic system). To determine
stabilities, we have developed methods for cleaving TM segments in vivo via native
intramembrane proteases. We have discovered that many S-SMPs are stable across the
membrane only because their periplasmic & cytoplasmic domains cannot cross the membrane.
We have also discovered that translocon-to-membrane transfer energetics are not equal to
membrane-to-cytoplasm transfer energetics and that stability depends upon growth
temperature. An important aspect of our work is the use of Molecular Dynamics simulations in
concert with experiments to understand the dynamics of the SecYEG translocon. Little is known
about SecA function at the atomic level despite hundreds of papers on the subject. Calling
upon our lab’s expertise in lipid-protein interactions, we have laid the foundation for electron
cryomicroscopic (cryo-EM) studies of the structure of SecA bound to lipid nanodiscs. Our
ambition is to obtain a complete structural view of the SecA-guided secretion process.
SWhite_Abstract_MIRA_2020.docx, 15 January 2020

## Key facts

- **NIH application ID:** 10086642
- **Project number:** 1R35GM139652-01
- **Recipient organization:** UNIVERSITY OF CALIFORNIA-IRVINE
- **Principal Investigator:** STEPHEN H. WHITE
- **Activity code:** R35 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $472,000
- **Award type:** 1
- **Project period:** 2021-06-01 → 2026-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10086642

## Citation

> US National Institutes of Health, RePORTER application 10086642, Membrane Protein Folding and Assembly (1R35GM139652-01). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10086642. Licensed CC0.

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