Miethke Marcus, Monteferrante Carmine G, Marahiel Mohamed A, van Dijl Jan Maarten
Department of Chemistry/Biochemistry, Philipps University Marburg, Marburg, Germany.
Biochim Biophys Acta. 2013 Oct;1833(10):2267-78. doi: 10.1016/j.bbamcr.2013.05.027. Epub 2013 Jun 10.
Efficient uptake of iron is of critical importance for growth and viability of microbial cells. Nevertheless, several mechanisms for iron uptake are not yet clearly defined. Here we report that the widely conserved transporter EfeUOB employs an unprecedented dual-mode mechanism for acquisition of ferrous (Fe[II]) and ferric (Fe[III]) iron in the bacterium Bacillus subtilis. We show that the binding protein EfeO and the permease EfeU form a minimal complex for ferric iron uptake. The third component EfeB is a hemoprotein that oxidizes ferrous iron to ferric iron for uptake by EfeUO. Accordingly, EfeB promotes growth under microaerobic conditions where ferrous iron is more abundant. Notably, EfeB also fulfills a vital role in cell envelope stress protection by eliminating reactive oxygen species that accumulate in the presence of ferrous iron. In conclusion, the EfeUOB system contributes to the high-affinity uptake of iron that is available in two different oxidation states.
高效摄取铁对于微生物细胞的生长和生存至关重要。然而，几种铁摄取机制尚未明确界定。在此我们报告，广泛保守的转运蛋白EfeUOB在枯草芽孢杆菌中采用了一种前所未有的双模式机制来获取亚铁（Fe[II]）和铁（Fe[III]）。我们表明，结合蛋白EfeO和通透酶EfeU形成了一个用于摄取铁的最小复合物。第三个组分EfeB是一种血红素蛋白，它将亚铁氧化为铁以便被EfeUO摄取。因此，EfeB在亚铁更丰富的微需氧条件下促进生长。值得注意的是，EfeB通过消除在亚铁存在时积累的活性氧，在细胞包膜应激保护中也发挥着至关重要的作用。总之，EfeUOB系统有助于高亲和力摄取两种不同氧化态的可用铁。
