Skaar Eric P, Gaspar Andrew H, Schneewind Olaf
Committee on Microbiology, University of Chicago, Chicago, Illinois 60637, USA.
J Biol Chem. 2004 Jan 2;279(1):436-43. doi: 10.1074/jbc.M307952200. Epub 2003 Oct 21.
Staphylococcus aureus requires iron for growth and utilizes heme as a source of iron during infection. Staphylococcal surface proteins capture hemoglobin, release heme from hemoglobin and transport this compound across the cell wall envelope and plasma membrane into the bacterial cytoplasm. Here we show that Staphylococcus aureus isdG and isdI encode cytoplasmic proteins with heme binding properties. IsdG and IsdI cleave the tetrapyrrol ring structure of heme in the presence of NADPH cytochrome P450 reductase, thereby releasing iron. Further, IsdI complements the heme utilization deficiency of a Corynebacterium ulcerans heme oxygenase mutant, demonstrating in vivo activity of this enzyme. Although Staphylococcus epidermidis, Listeria monocytogenes, and Bacillus anthracis encode homologues of IsdG and IsdI, these proteins are not found in other bacteria or mammals. Thus, it appears that bacterial pathogens evolved different strategies to retrieve iron from scavenged heme molecules and that staphylococcal IsdG and IsdI represent examples of bacterial heme-oxygenases.
金黄色葡萄球菌生长需要铁，并在感染期间利用血红素作为铁源。葡萄球菌表面蛋白捕获血红蛋白，从血红蛋白中释放血红素，并将这种化合物穿过细胞壁包膜和质膜转运到细菌细胞质中。在此我们表明，金黄色葡萄球菌isdG和isdI编码具有血红素结合特性的细胞质蛋白。在存在NADPH细胞色素P450还原酶的情况下，IsdG和IsdI会切割血红素的四吡咯环结构，从而释放铁。此外，IsdI弥补了溃疡棒状杆菌血红素加氧酶突变体的血红素利用缺陷，证明了该酶在体内的活性。虽然表皮葡萄球菌、单核细胞增生李斯特菌和炭疽芽孢杆菌编码IsdG和IsdI的同源物，但在其他细菌或哺乳动物中未发现这些蛋白。因此，细菌病原体似乎进化出了不同的策略来从 scavenged血红素分子中获取铁，并且葡萄球菌的IsdG和IsdI代表了细菌血红素加氧酶的例子。
