# Equipment Supplement R01GM126626: Mechanistic studies of prokaryotic and eukaryotic nitrate/nitrite transport

> **NIH NIH R01** · UNIVERSITY OF COLORADO DENVER · 2021 · $71,915

## Abstract

Recent studies suggest that nitrate and nitrite molecules have profound beneficial effects to human
health, though they were thought to be cancerous since 1970s. To maximize their pharmaceutical
potential, we need to first understand how nitrate and nitrite circulate in humans. Such circulation
depends on two critical events: active accumulation of nitrate mediated by sialin transporters in salivary
glands, as well as nitrate uptake and nitrite secretion by commensal bacteria in the mouth. Thus,
nitrate/nitrite molecules have to cross different cellular membranes multiple times, before being used
by humans. These translocation processes are mediated by a group of membrane proteins called
nitrate transporters. To understand how these transporters function, we solved high-resolution crystal
structures of NarK from E. coli, and further demonstrated that, surprisingly, NarK is a nitrate/nitrite
exchanger. Despite the progress we made, the detailed molecular mechanisms of nitrate/nitrite
translocation are still largely unknown. In this proposal, we aim to fill the knowledge gap by: 1)
understand substrate selectivity and conformational flexibility using directed-mutagenesis of NarK, so
to better understand the function of NarK at the molecular level; 2) obtain high-resolution structures of
NarK in previously unobserved conformation, so we can reconstruct the complete transport cycle of
NarK; 3) explore the structure-function relationship of human nitrate transporter sialin, so we will
understand the similarities and differences among nitrate transporters from diverse species. Overall,
upon completion of the proposal, we expect to expand our general understanding of the nitrate/nitrite
transport and shed light on the crucial roles that nitrate transporters (both eukaryotic and prokaryotic)
play in nitrate/nitrite circulation. The knowledge gained here will facilitate potential drug development
related to bacterial nitrate transporters and human sialin.

## Key facts

- **NIH application ID:** 10377771
- **Project number:** 3R01GM126626-04S1
- **Recipient organization:** UNIVERSITY OF COLORADO DENVER
- **Principal Investigator:** Hongjin Zheng
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $71,915
- **Award type:** 3
- **Project period:** 2018-01-01 → 2022-11-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10377771

## Citation

> US National Institutes of Health, RePORTER application 10377771, Equipment Supplement R01GM126626: Mechanistic studies of prokaryotic and eukaryotic nitrate/nitrite transport (3R01GM126626-04S1). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10377771. Licensed CC0.

---

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