National Academy of Sciences, Proceedings of the National Academy of Sciences, 27(113), p. 7539-7544, 2016
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Significance All heme-dependent functions require the mobilization of labile heme (LH), of which there is little understanding of its nature and dynamics. To probe LH pools, we developed genetically encoded fluorescent heme sensors and deployed them in the unicellular eukaryote Saccharomyces cerevisiae . We find that LH is relatively abundant in the cytosol, but exceedingly low in the mitochondria and nucleus. Further, we find that LH can be mobilized by signaling molecules like nitric oxide. We also find that the glycolytic enzyme glyceraldehyde phosphate dehydrogenase constitutes a major heme buffer and is responsible for regulating the activity of a heme-dependent transcription factor. Altogether, our work will have profound implications for understanding the mechanisms of heme utilization.