Heme dynamics and trafficking factors revealed by genetically encoded fluorescent heme sensors

Proc Natl Acad Sci U S A. 2016 Jul 5;113(27):7539-44. doi: 10.1073/pnas.1523802113. Epub 2016 May 31.


Heme is an essential cofactor and signaling molecule. Heme acquisition by proteins and heme signaling are ultimately reliant on the ability to mobilize labile heme (LH). However, the properties of LH pools, including concentration, oxidation state, distribution, speciation, and dynamics, are poorly understood. Herein, we elucidate the nature and dynamics of LH using genetically encoded ratiometric fluorescent heme sensors in the unicellular eukaryote Saccharomyces cerevisiae We find that the subcellular distribution of LH is heterogeneous; the cytosol maintains LH at ∼20-40 nM, whereas the mitochondria and nucleus maintain it at concentrations below 2.5 nM. Further, we find that the signaling molecule nitric oxide can initiate the rapid mobilization of heme in the cytosol and nucleus from certain thiol-containing factors. We also find that the glycolytic enzyme glyceraldehyde phosphate dehydrogenase constitutes a major cellular heme buffer, and is responsible for maintaining the activity of the heme-dependent nuclear transcription factor heme activator protein (Hap1p). Altogether, we demonstrate that the heme sensors can be used to reveal fundamental aspects of heme trafficking and dynamics and can be used across multiple organisms, including Escherichia coli, yeast, and human cell lines.

Keywords: glyceraldehyde phosphate dehydrogenase; heme dynamics; heme sensors; heme trafficking; nitric oxide.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biosensing Techniques*
  • Escherichia coli
  • Glyceraldehyde-3-Phosphate Dehydrogenases / metabolism
  • HEK293 Cells
  • Heme / metabolism*
  • Humans
  • Nitric Oxide / metabolism
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins / metabolism
  • Transcription Factors / metabolism


  • Hap1p protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Transcription Factors
  • Nitric Oxide
  • Heme
  • Glyceraldehyde-3-Phosphate Dehydrogenases