# Mechanisms of Ion Channels and Enzymatic Membrane Proteins

> **NIH NIH R35** · SLOAN-KETTERING INST CAN RESEARCH · 2024 · $950,400

## Abstract

PROJECT SUMMARY
The objectives of this research program are to understand the structural, functional, and molecular
mechanisms of two classes of integral membrane proteins in eukaryotes: ion channels and enzymes that
catalyze chemical reactions within lipid membranes. For ion channels, we aim to discover the mechanisms by
which the channels conduct ions across cellular membranes, achieve ion selectivity, and are gated. Regarding
membrane enzymes, the salient questions we will address include how both water-soluble and lipophilic
substrates access membrane-embedded active sites, what underlies chemical mechanisms of catalysis, what
conformational changes occur during the reaction cycles, and what constraints the lipid membrane places on
these processes. We combine approaches to determine three-dimensional structures (X-ray crystallography
and cryo-electron microscopy) with functional analyses (e.g. electrophysiology, enzymology, and biochemistry)
to pursue holistic mechanistic understandings of these complex molecular machines.
The ion channels under study include the mitochondrial calcium uniporter, the bestrophin (BEST) family of
calcium-activated chloride channels, and two-pore domain potassium (K2P) channels. The mitochondrial
calcium uniporter is a highly regulated multi-subunit ion channel complex. It is the primary conduit for
mitochondrial calcium entry and thereby regulates ATP synthesis and other processes. Our efforts are aimed
to discover the channel’s modes of ion selectivity and gating, and to investigate functions of its regulatory
subunits. BEST channels form anion-selective pores that are regulated by intracellular calcium,
phosphorylation, and changes in cell volume. Mutations in BEST channels cause retinal degenerative
diseases. Our efforts are geared to understand the gating and selectivity properties of the channels, with
particular attention to: differences among human BEST1-4 channels, interactions with binding partners (e.g.
lipids and other proteins), and the possibility that the channels conduct neurotransmitters. K2P channels
establish the resting potential of cells and thereby regulate immune responses and neuronal firing. We aim to
determine the structures and mechanisms of the channels, with emphasis on regulation by cellular binding
partners.
Regarding our studies of integral membrane enzymes, current focuses are the enzymes ICMT and RCE1,
which catalyze posttranslational modifications of RAS and other CAAX proteins, and the enzymes HHAT and
GOAT, which attach acyl groups onto the signaling molecules Hedgehog and ghrelin. We aim to determine
atomic structures of these enzymes with substrates, substrate analogs, and products that represent snapshots
of their reaction coordinates – and to combine these efforts with experiments that address function.
The studies will reveal principles of ion channel and enzyme function, thereby making substantial contributions
to the understandings of the physiological processes that th...

## Key facts

- **NIH application ID:** 10841874
- **Project number:** 2R35GM131921-06
- **Recipient organization:** SLOAN-KETTERING INST CAN RESEARCH
- **Principal Investigator:** Stephen Barstow Long
- **Activity code:** R35 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $950,400
- **Award type:** 2
- **Project period:** 2019-04-01 → 2029-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10841874

## Citation

> US National Institutes of Health, RePORTER application 10841874, Mechanisms of Ion Channels and Enzymatic Membrane Proteins (2R35GM131921-06). Retrieved via AI Analytics 2026-05-27 from https://api.ai-analytics.org/grant/nih/10841874. Licensed CC0.

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