# Biological and structural characterization of the Type 3 fimbrial subunit MrkA from Klebsiella pneumoniae

## TL;DR

This paper studies the structure of MrkA, a key protein in Klebsiella pneumoniae fimbriae, to explore its potential as a vaccine target.

## Contribution

The study provides the first detailed structural characterization of the MrkA protein using NMR spectroscopy.

## Key findings

- The three-dimensional structure of MrkA was elucidated using solution-state NMR.
- Monoclonal antibodies recognizing MrkA oligomers also bind recombinant MrkA protein.
- The findings support MrkA as a potential target for vaccine development against K. pneumoniae.

## Abstract

Klebsiella pneumoniae is a Gram‐negative opportunistic pathogen responsible for a wide range of community‐associated and hospital‐acquired infections and a major cause of neonatal sepsis in low‐ and middle‐income countries. The pathogen's surface fimbriae, particularly the Type 3 fimbriae, are critical for bacterial adhesion, biofilm formation, and host defense evasion. MrkA, the pathogen's major Type 3 fimbrial subunit, has a structural function in fimbrial assembly, but its three‐dimensional structure remains to be fully elucidated. In this study, we utilized solution‐state nuclear magnetic resonance spectroscopy to elucidate the structure of MrkA, leveraging previously reported chemical shift assignments of a designed self‐complementing monomeric protein. Additionally, we confirmed the ability of monoclonal antibodies, capable of recognizing MrkA oligomers on wild‐type Klebsiella bacteria, to bind the recombinant MrkA protein. Our findings contribute to the evaluation of MrkA as a potential target in vaccine development against Klebsiella pneumoniae infections.