# Full-length inhibitor protein is the most effective to perturb human dUTPase activity

## TL;DR

Researchers found that the full-length version of a protein inhibitor is most effective at blocking the activity of the human dUTPase enzyme.

## Contribution

The study reveals the C-terminal region of the inhibitor is crucial for maximal dUTPase inhibition.

## Key findings

- The crystal structure of the StlNT domain in complex with dUTPase was determined.
- Point mutants based on the structure improved inhibition effectiveness.
- The full-length Stl protein is required for maximum inhibition of dUTPase.

## Abstract

It has been demonstrated recently that knockout of the dUTPase enzyme leads to early embryonic lethality in mice. However, to explore the physiological processes arising upon the lack of dUTPase an effective and selective enzyme inhibitor is much needed. A highly specific and strong binding proteinaceous human dUTPase inhibitor described by us recently was a promising starting point to develop a molecular tool to study temporal and conditional dUTPase inhibition in cellulo. Towards this end we determined the 3D crystal structure of the crystallizable amino terminal domain of inhibitor protein, named StlNT in complex with the human dUTPase and designed several point mutants based on the structure to improve the inhibition effectivity. The effect of StlNT and a peptide derived from the full-length inhibitor on the activity of the human dUTPase was also tested. We showed that the C-terminal part of the Stl protein omitted from the crystal structure has an important role in the enzyme inhibition as the full-length Stl is needed to exert maximal inhibition on the human dUTPase.

The online version contains supplementary material available at 10.1038/s41598-025-86131-7.