HrtBA and menaquinones control haem homeostasis in Lactococcus lactis
HrtBA and menaquinones control haem homeostasis in Lactococcus lactis
复制标题
DOI：
10.1111/mmi.12705
复制
发表时间：
2014-08-01
影响因子：
3.6
通讯作者：
Lechardeur, Delphine
中科院分区：
文献类型：
--
作者：
Joubert, Laetitia;Derre-Bobillot, Aurelie;Lechardeur, Delphine
乳酸乳球菌是一种广泛用于乳制品生产的革兰氏阳性发酵菌。在缺乏血红素生物合成基因的情况下，乳酸乳杆菌仍然可以通过在曝气培养中加入血红素时，通过激活末端细胞色素BD氧化酶来转变为能量有利的呼吸代谢。Hem的细胞内动态平衡是由编码保守的膜HrtBA血红素外排通透酶的hrtRBA操纵子和独特的细胞内HrtR感受器和调节因子介导的。在这里，我们报告了膜相关的孟喹酮(MK)有利于在膜上积累还原的血红素。氧提供的氧化环境阻止和逆转了MK对Hamin的还原，从而限制了血红素在膜中的积累。HrtBA可抵消MK依赖的膜对膜中多余的血红素的滞留，提示从这个隔室直接外流。此外，HrtBA和MK介导的还原都对HrtR Hem传感器诱导的HrtR Hem传感器诱导的细胞内Hem池产生强烈影响，这表明细胞内HrtBA的获取是在膜水平上控制的，不需要专门的输入系统。我们的结论导致了一种新的假说，即HrtBA和细菌膜在乳酸乳杆菌中起着核心作用。
Lactococcus lactis is a fermenting Gram-positive bacterium widely used for production of dairy products. Lacking haem biosynthesis genes, L. lactis can still shift to an energetically favourable respiratory metabolism by activating a terminal cytochrome bd oxidase when haem is added to an aerated culture. Haem intracellular homeostasis is mediated by the hrtRBA operon encoding the conserved membrane HrtBA haem efflux permease and the unique intracellular haem sensor and regulator, HrtR. Here we report that membrane-associated menaquinones ( MK) favour the accumulation of reduced haem in membranes. An oxidative environment, provided by oxygen, prevents and reverses haemin reduction by MK and thus limits haem accumulation in membranes. HrtBA counteracts MK-dependent membrane retention of excess haem in membrane, suggesting direct efflux from this compartment. Moreover, both HrtBA and MK-mediated reduction have a strong impact on haem intracellular pools, as determined via HrtR haem sensor induction, suggesting that intracellular haem acquisition is controlled at the membrane level without the need for dedicated import systems. Our conclusions lead to a new hypothesis of haem acquisition and regulation in which HrtBA and the bacterial membrane have central roles in L. lactis.