# The Trimeric Autotransporter Adhesin EmaA and Infective Endocarditis

## TL;DR

This paper explores how the protein EmaA helps a specific type of bacteria cause heart infection by sticking to tissues.

## Contribution

The paper provides insights into the biochemical and structural roles of EmaA in the pathogenicity of Aggregatibacter actinomycetemcomitans.

## Key findings

- EmaA is a nonfimbrial adhesin involved in the initiation of infective endocarditis.
- EmaA interacts with extracellular matrix components, contributing to bacterial pathogenicity.
- The protein's sequence varies by bacterial serotype, affecting its function.

## Abstract

Infective endocarditis (IE), a disease of the endocardial surface of the heart, is usually of bacterial origin and disproportionally affects individuals with underlying structural heart disease. Although IE is typically associated with Gram-positive bacteria, a minority of cases are caused by a group of Gram-negative species referred to as the HACEK group. These species, classically associated with the oral cavity, consist of bacteria from the genera Haemophilus (excluding Haemophilus influenzae), Aggregatibacter, Cardiobacterium, Eikenella, and Kingella. Aggregatibacter actinomycetemcomitans, a bacterium of the Pasteurellaceae family, is classically associated with Aggressive Periodontitis and is also concomitant with the chronic form of the disease. Bacterial colonization of the oral cavity serves as a reservoir for infection at distal body sites via hematological spreading. A. actinomycetemcomitans adheres to and causes disease at multiple physiologic niches using a diverse array of bacterial cell surface structures, which include both fimbrial and nonfimbrial adhesins. The nonfimbrial adhesin EmaA (extracellular matrix binding protein adhesin A), which displays sequence heterogeneity dependent on the serotype of the bacterium, has been identified as a virulence determinant in the initiation of IE. In this chapter, we will discuss the known biochemical, molecular, and structural aspects of this protein, including its interactions with extracellular matrix components and how this multifunctional adhesin may contribute to the pathogenicity of A. actinomycetemcomitans.