Eukaryotic Heme Utilization

关于血红素在真核生物中的转运知之甚少，并且在酵母中还没有鉴定出血红素特异性转运摄取系统。虽然S.虽然酿酒酵母对铁缺乏没有反应，但我们已经确定该物种确实具有在血红素缺乏和缺氧条件下激活的诱导型血红素摄取系统。我们对在这些条件下生长的菌株进行了微阵列分析，发现许多推定的转运蛋白被转录激活。我们已经确定了转运蛋白，当过度表达，增加血红素摄取到酵母。我们还确定了一种转运蛋白，称为PUG 1（卟啉摄取基因1），它刺激血红素的直接前体原卟啉IX的摄取，同时抑制血红素的利用。这种转运蛋白在缺氧和血红素缺乏时被转录激活，并在酵母的质膜上表达。 我们与马里兰州大学的伊克巴尔·哈姆扎合作，对C.通过在酵母中表达它们。血红素调节基因来自C. elegans将被克隆到酵母表达载体中，并分析血红素摄取活性及其对细胞内血红素库的影响。

Very little is known about heme transport in eukaryotes and a heme-specific transport uptake systems have not been identified in yeast. Although S. cerevisiae does not take up heme in response to iron deprivation, we have determined that this species does have an inducible heme uptake system that is activated under heme deficiency and hypoxic conditions. We performed microarray analysis of strains grown under these conditions, and found that a number of putative transporters are transcriptionally activated. We have identified transporters that, when over expressed, increase heme uptake into yeast. We have also identified a transporter, termed PUG1 (Porphyrin uptake gene 1), that stimulates the uptake of protoporphyrin IX, the immediate precursor of heme, and simultaneously inhibits the utilization of heme. This transporter is transcriptionally activated by oxygen and heme deficiency and is expressed on the plasma membrane of yeast. In collaboration with Iqbal Hamza of the University of Maryland, we are functionally characterizing the putative heme transporters of C. elegans by expressing them in yeast. Heme regulated genes from C. elegans will be cloned into yeast expression vectors and analyzed for heme uptake activity and their effects on intracellular pools of heme.