# Structural and Functional Basis of the Vitamin K Cycle

> **NIH NIH R01** · WASHINGTON UNIVERSITY · 2024 · $604,889

## Abstract

Project Summary
The vitamin K cycle supports blood coagulation, bone mineralization, and vascular calcium homeostasis. The
activity of vitamin-K-dependent proteins (e.g., coagulation factors) is regulated by the γ-carboxylase, GGCX.
Epoxidation of vitamin K hydroquinone (KH2) drives catalysis of GGCX and is regenerated by vitamin K epoxide
reductase (VKOR) with the assistance of a VKORL paralog and FSP1. VKOR is targeted by warfarin, a widely
used oral anticoagulant whose overdose often leads to severe bleeding. Due to poor mechanistic understandings,
modulation of the vitamin K cycle to improve anticoagulation therapy has not been explored. In addition, FSP1
regulates ferroptosis by producing KH2, which also affords potent protection against lipid peroxidation. However,
the roles of vitamin K reductases in coagulation and ferroptosis, which are linked to numerous cardiovascular
disorders, are unclear. Further, the mechanisms of the tightly regulated GGCX catalysis remain elusive. Thus,
there is a need to establish a deeper understanding of the entire vitamin K cycle and the biology underlying blood
coagulation so new therapeutic strategies can be developed for thromboembolic and cardiovascular diseases.
Our long-term goal is to elucidate the physiological process of the entire vitamin K cycle and the underlying
mechanisms. The objective of this renewal application is to modulate the redox state of VKOR to regulate
anticoagulation, elucidate the relative contributions of VKOR, VKORL and FSP1 to support coagulation and
control ferroptosis, and understand the structural mechanisms of GGCX catalysis. Our hypotheses are: (1)
shifting VKOR towards a reduced state enhances vitamin K antidoting by increasing VKOR activity and
facilitating warfarin release; (2) VKOR/VKORL are primarily responsible for K antidoting and reducing lipid
peroxidation in the ER; and (3) GGCX binding of substrates induces conformational changes to tightly regulate
the sequential reactions. Our preliminary data obtained 11 crystal structures of VKOR and a VKORL paralog
with substrates and antagonists at different redox states. We also discovered that VKOR at reduced state is
highly active but poorly inhibited by warfarin, and that K competition at partially oxidized state releases warfarin.
We showed that VKOR/VKORL better support carboxylation and K antidoting relative to FSP1. We identified
VKOR partner proteins and showed that reduced glutathione maintains VKOR activity. We obtained the first
cryo-EM structures of human and conus GGCX that suggests keto-enol tautomerization as an elegant solution
that couples epoxidation and carboxylation across the membrane interface. Armed with our expertise in the
vitamin K cycle and membrane proteins, we will test our hypotheses with three specific aims: (1) Identify new
anticoagulation strategies by employing VKOR redox states; (2) elucidate the interplay of the vitamin K cycle in
γ-carboxylation and ferroptosis; and (3) understand the s...

## Key facts

- **NIH application ID:** 10803626
- **Project number:** 2R01HL121718-10A1
- **Recipient organization:** WASHINGTON UNIVERSITY
- **Principal Investigator:** Weikai Li
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $604,889
- **Award type:** 2
- **Project period:** 2014-05-15 → 2027-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10803626

## Citation

> US National Institutes of Health, RePORTER application 10803626, Structural and Functional Basis of the Vitamin K Cycle (2R01HL121718-10A1). Retrieved via AI Analytics 2026-06-01 from https://api.ai-analytics.org/grant/nih/10803626. Licensed CC0.

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