<i>Moraxella catarrhalis</i> HemW is a Heme-binding Radical SAM Enzyme

<i>Moraxella catarrhalis</i> is an emerging human respiratory pathogen responsible for a significant proportion of childhood otitis media and exacerbations of chronic obstructive pulmonary disease. Recent transposon sequencing analysis identified <i>yggW</i> (renamed as <i>hemW</i> ), an uncharacterized gene, as essential for <i>M. catarrhalis</i> growth under iron-limiting conditions, mimicking host-imposed nutritional immunity. HemW is annotated as a putative radical <i>S</i> -adenosylmethionine (SAM) enzyme and belongs to the HemN-like subfamily, but its biochemical properties remain unclear. Here, we report on the first experimental characterizations of <i>Mc</i> HemW. Our bioinformatic analysis confirmed its evolutionary relationship with the putative heme-binding radical SAM enzyme <i>Ec</i> HemW in <i>Escherichia coli</i> . Using biochemical and spectroscopic approaches, we demonstrate that <i>Mc</i> HemW contains a catalytically active [4Fe-4S] cluster and binds heme <i>in vitro</i> . These findings support a functional role for <i>Mc</i> HemW as a putative heme chaperone, highlighting it as a potential target for disrupting iron metabolism in this clinically important pathogen.