# Archaeal heme a synthase: evolutionary trajectory distinct from bacterial homologs

## TL;DR

This paper explores how heme a synthase evolved differently in archaea compared to bacteria, revealing distinct evolutionary patterns and complexity.

## Contribution

The study provides new insights into the evolutionary divergence of heme a synthase in archaea from bacterial homologs.

## Key findings

- Types 1 and 2 of heme a synthase diverged early in the evolutionary history of archaea.
- The evolution of heme a synthase reflects both ancestral innovations and recent ecological pressures.
- Archaeal heme a synthase shows distinct evolutionary patterns compared to bacterial versions.

## Abstract

Hemes are iron-containing porphyrin compounds that play a crucial role in a wide array of biological processes. Heme a synthase (HAS) is a crucial enzyme that facilitates the biosynthesis of heme a, an essential heme variant that serves as a cofactor in heme-copper terminal oxidases and in some acidophilic archaea's quinol reductases, such as the ba complex. Depending on the length and presence or absence of cysteine residues in the periplasmic loop(s), HAS has been classified into different types. Our manuscript presents a large-scale analysis of the distribution and evolution of HAS in Archaea in comparison to Bacteria, revealing evolutionary patterns among the proposed subtypes, with types 1 and 2 diverging early. This study also underscores the complexity of HAS enzyme evolution, which reflects deep ancestral innovations as well as recent ecological pressures.