Heme (iron protoporphyrin IX) concentration

Range in cytosol 20 - 40nM: in nucleus & mitochondria <2.5nM: total ferrous heme in mitochondria ~30µM
Organism Budding yeast Saccharomyces cerevisiae
Reference Hanna DA et al., 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 abstract & p.7539 left column bottom paragraph & p.7543 left column 4th paragraph & bottom paragraphPubMed ID27247412
Primary Source [28] Garber Morales J, et al. (2010) Biophysical characterization of iron in mitochondria isolated from respiring and fermenting yeast. Biochemistry 49(26):5436–5444 doi: 10.1021/bi100558zPubMed ID20536189
Method Abstract: "Herein, [investigators] elucidate the nature and dynamics of LH (labile heme) using genetically encoded ratiometric fluorescent heme sensors in the unicellular eukaryote Saccharomyces cerevisiae."
Comments Abstract: "[Investigators] find that the subcellular distribution of LH (labile heme) is heterogeneous, the cytosol maintains LH at ∼20-40 nM, whereas the mitochondria and nucleus maintain it at concentrations below 2.5 nM." P.7539 left column bottom paragraph: "Herein, [investigators] report genetically encoded ratiometric fluorescent heme sensors and deploy them in the unicellular eukaryote Saccharomyces cerevisiae (Baker’s yeast) to elucidate the nature and dynamics of LH. [They] find that LH is buffered at a concentration of 20–40 nM in the cytosol and less than 2.5 nM in the nucleus and mitochondria." P.7543 left column bottom paragraph: "The mitochondria, which have a very high demand for heme and are the site of heme biosynthesis, have exceptionally low quantities of LH, less than 2.5 nM or fewer than one molecule. By comparison, total ferrous heme in the yeast mitochondria has been estimated to be ∼30 μM, or ∼9,000 molecules (primary source). Taken together, this low amount of mitochondrial LH suggests that mitochondrial heme is tightly regulated and trafficked in a manner that limits its availability. This observation is consistent with the identification of mitochondrial heme metabolism complexes that traffic heme via transient protein–protein interactions, thereby circumventing the LH pool (ref 35)."
Entered by Uri M
ID 114002