# Photochemical determination of sodium channel voltage-dependent gating and composition

> **NIH NIH R01** · UNIVERSITY OF IOWA · 2020 · $339,281

## Abstract

Voltage-gated sodium channels (NaVs) maintain the electrical cadence of neurons and muscle tissues by
selectively controlling the rapid inward passage of their namesake ion. The essential NaV complex is
comprised of a 260-kDa pore-forming alpha subunit (encoded by NaV1.1-1.9) that is partnered with beta
subunits (1–4). Defects in sodium channel function resulting from inherited mutations or channel
dysmodulation are established causes of human disease, and are associated with sudden infant death,
arrhythmia and pain-causing syndromes. While there is an urgent need to better understand the molecular
basis for perturbed NaV function, there are few research tools available to obtain these insights, and these
persistent technical barriers slow the pace of discovery in the study of many types of and membrane proteins.
NaVs have begun to benefit from atomic-resolution structures of related bacterial NaVs, but in addition to their
evolved differences from eukaryotic channels, these proteins are analyzed in the absence of membrane
voltage and thus the relevance of the conformations examined is unclear. For eukaryotic NaVs, key
unaddressed issues include structural differences between the resting and inactivated channel states, the
mechanism of inactivation and the role of the C-terminus, the impact of inherited mutations on molecular gating
events, and the molecular basis of the NaV channel regulation by -subunits. We have developed a number of
complementary chemical biology research tools that will provide essential new information about the function
of NaVs: (a) We have streamlined the used of genetically encoded cross-linking amino acids with novel click-
chemistry functionality that, when used in combination with mass spectrometry, enables the discovery of
transient inter- and intra-peptide interaction networks in live cells. (b) We have developed a powerful new
approach whereby Cy3 and Cy5 are encoded as unnatural amino acids into membrane proteins in live cells.
This approach will allow for encoded single molecule fluorescence resonance energy transfer (smFRET) and
the direct measurement of electrically silent conformational dynamics of membrane proteins in a live cell under
voltage control. (c) An all-atom computational model of the eukaryotic NaV that will guide and support our
efforts to determine conformational movement and non-covalent interactions in NaVs. We propose to: (1)
advance the mechanistic understanding of sodium channel gating, with a focus on inactivation given its
outsized role in human disease, and the conformational differences and energetic coupling between resting
and inactivated conformations; (2) obtain an optically generated relative distance map of key gating states of
single NaVs and how these distances are effected by disease causing mutations; and (3) provide the basis of
-subunit regulation, including the molecular identification of interaction sites and mechanisms of disease
causing mutations. These three aims are...

## Key facts

- **NIH application ID:** 10004154
- **Project number:** 5R01GM122420-04
- **Recipient organization:** UNIVERSITY OF IOWA
- **Principal Investigator:** Christopher A Ahern
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $339,281
- **Award type:** 5
- **Project period:** 2017-09-20 → 2022-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10004154

## Citation

> US National Institutes of Health, RePORTER application 10004154, Photochemical determination of sodium channel voltage-dependent gating and composition (5R01GM122420-04). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/10004154. Licensed CC0.

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