# Structure-Function Relationship study of HupZ

> **NIH NIH F31** · UNIVERSITY OF TEXAS SAN ANTONIO · 2024 · $40,174

## Abstract

Abstract
A heme utilization protein operon hupYZ encoding periplasmic proteins has recently been identified from
Streptococcus pyogenes, a significant pathogen involved in a wide range of diseases. One of the encoded
proteins, HupZ, was initially assigned as a heme oxygenase. However, our study revealed that this weak activity
was due to a poly‐His‐tag induced structural similarity with the active site of genuine heme oxygenases. The
tag‐free HupZ does not degrade heme; however, we recently discovered that tag‐free HupZ binds FMN. The
FMN‐bound HupZ crystal structure superimposes with the biliverdin reductase (BVR) recently found in
Mycobacterium tuberculosis (Mtb) that utilizes an F420H2 cofactor. The flavin moiety of FMN in HupZ aligns well
with the deazaflavin moiety of the F420H2 cofactor. Therefore, we propose that HupZ is a flavin/deazaflavin
oxidoreductase (FDOR) dependent BVR in the heme utilization pathway (Hup) of Streptococcus. Structural and
functional characterizations are proposed to further the molecular understanding of this Hup protein using
biochemical, spectroscopic, and structural approaches. We will interrogate how tag‐free HupZ interacts with
its cofactor and substrate, and we will determine the critical residues involved in biliverdin reduction. We will
attempt to characterize catalytic intermediates and elucidate the catalytic mechanism. Completing the
proposed biochemical and structural studies will fill the gaps in our current understanding of the heme
utilization pathway in a significant pathogen. Only a few FDOR‐dependent enzymes have been described, and
the F420H2‐dependent BVR mechanism remains to be elucidated; therefore, this work is also highly significant
to mechanistic enzymology.

## Key facts

- **NIH application ID:** 10863866
- **Project number:** 5F31GM145187-03
- **Recipient organization:** UNIVERSITY OF TEXAS SAN ANTONIO
- **Principal Investigator:** Ephrahime Traore
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $40,174
- **Award type:** 5
- **Project period:** 2022-07-01 → 2025-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10863866

## Citation

> US National Institutes of Health, RePORTER application 10863866, Structure-Function Relationship study of HupZ (5F31GM145187-03). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10863866. Licensed CC0.

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