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。 血红素是在线粒体中合成的，而辅因子则在整个细胞的各个区域中使用。血红素是高度疏水性的，并且不太可能被释放到胞质溶胶的水性环境中，这表明存在血红素的细胞内运输的机制。我们已经设计了一个遗传筛选，用于鉴定参与细胞内血红素运输的酵母蛋白，并正在评估候选人。在这个屏幕上确定的基因表明，血红素从线粒体移动到其他网站通过囊泡运输系统。 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。血红素转运蛋白C.当在酵母中表达时，秀丽线虫具有血红素摄取活性，并且当在酵母中表达时，血红素转运蛋白的突变形式表现出功能丧失。

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. Heme is synthesized in mitochondria, yet the cofactor is used in compartments throughout the cell. Heme is highly hydrophobic and is unlikely to be released into the aqueous environment of the cytosol, suggesting that mechanisms exist for the intracellular trafficking of heme. We have designed a genetic screen for the identification of yeast proteins involved in intracellular heme trafficking and are evaluating candidates. Genes identified in this screen suggest that heme moves from the mitochondria to other sites through the vesicular trafficking system. 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 transporters from C. elegans have heme uptake activity when expressed in yeast and mutant forms of heme transporters exhibit loss of function when expressed in yeast.