Related Experiment Video

Updated: Aug 24, 2026

Measurement of Heme Synthesis Levels in Mammalian Cells
09:43

Measurement of Heme Synthesis Levels in Mammalian Cells

Published on: July 9, 2015

Characterization of a Heme-Binding Radical SAM Enzyme HemW from Moraxella catarrhalis

Caitlin M Padgett1, Melissa M Bollmeyer2, Kaleb Boswinkle3

  • 1Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States.

ACS Bio & Med Chem Au
|August 22, 2026
PubMed

Insights

Moraxella catarrhalis HemW (McHemW) is essential for growth under iron limitation. This study reveals McHemW binds heme via a unique domain, offering insights into bacterial iron acquisition.

Area of Science:

  • Biochemistry
  • Microbiology
  • Molecular Biology

Background:

  • Moraxella catarrhalis is a significant respiratory pathogen.
  • The hemW gene is crucial for M. catarrhalis growth in low-iron environments, mimicking host nutritional immunity.
  • The biochemical function of HemW, a radical S-adenosylmethionine enzyme, is largely unknown.

Purpose of the Study:

  • To biochemically characterize Moraxella catarrhalis HemW (McHemW).
  • To elucidate the mechanism of heme binding and its role in iron acquisition.
  • To understand the structural basis for heme recognition in HemW enzymes.

Main Methods:

  • Bioinformatic analysis to confirm evolutionary relationships.
  • Biochemical assays and spectroscopy to detect [4Fe-4S] cluster and heme binding.
  • Hydrogen-deuterium exchange mass spectrometry (HDX-MS) to map the heme-binding site.

Main Results:

  • McHemW possesses a catalytically active [4Fe-4S] cluster.
  • Experimental evidence confirms McHemW binds heme.
  • HDX-MS identified the heme-binding site within the C-terminal auxiliary domain, unique to HemW.

Conclusions:

  • McHemW is a heme-binding radical SAM enzyme.
  • The C-terminal domain is critical for heme recognition in McHemW.
  • These findings provide mechanistic insights into M. catarrhalis pathogenicity under iron-limited conditions.
Keywords:
EPRHDX-MSHemWHemeiron−sulfur clusterradical SAM enzyme

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