The HtrA/DegP family protease MamE is a bifunctional protein with roles in magnetosome protein localization and magnetite biomineralization.
The HtrA/DegP family protease MamE is a bifunctional protein with roles in magnetosome protein localization and magnetite biomineralization.
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DOI：
10.1111/j.1365-2958.2011.07631.x
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发表时间：
2011-05
影响因子：
3.6
通讯作者：
Komeili A
中科院分区：
文献类型：
--
作者：
Quinlan A;Murat D;Vali H;Komeili A
趋磁细菌含有纳米大小的膜结合细胞器，称为磁小体，其任务是将氧化铁磁铁矿的小晶体生物矿化，使生物体能够利用地磁力线进行导航。HtrA/DegP家族蛋白酶MamE在这一过程中起着关键作用。在其缺失的情况下，Magnetospirillum magneticum str AMB-1能够形成磁小体膜，但不能形成磁铁矿晶体，这一缺陷先前与磁小体蛋白的错误定位有关。在这项工作中，我们使用定向遗传方法发现MamE和另一种预测的磁小体相关蛋白酶MamO可能在体内发挥蛋白酶的功能。然而，与没有观察到生物矿化的mamE完全丧失相反，该蛋白的蛋白酶缺陷变体仍然支持小的，20纳米大小的磁铁矿晶体的起始和形成，太小而无法保持永久磁偶极矩。该分析还表明，MamE是一种双功能蛋白，在磁小体蛋白定位中具有蛋白酶独立作用，在小磁铁矿晶体成熟中具有蛋白酶依赖作用。总之，这些结果表明，在生物矿化过程中存在一个以前未被认识到的“检查点”，其中MamE调节磁铁矿形成的完成，从而将趋磁性作为生物体导航环境的主要模式。
Magnetotactic bacteria contain nanometer-sized, membrane-bound organelles, called magnetosomes, which are tasked with the biomineralization of small crystals of the iron oxide magnetite allowing the organism to use geomagnetic field lines for navigation. A key player in this process is the HtrA/DegP family protease MamE. In its absence, Magnetospirillum magneticum str AMB-1 is able to form magnetosome membranes but not magnetite crystals, a defect previously linked to the mislocalization of magnetosome proteins. In this work we use a directed genetic approach to find that MamE, and another predicted magnetosome-associated protease, MamO, likely function as proteases in vivo. However, as opposed to the complete loss of mamE where no biomineralization is observed, the protease-deficient variant of this protein still supports the initiation and formation of small, 20 nm-sized crystals of magnetite, too small to hold a permanent magnetic dipole moment. This analysis also reveals that MamE is a bifunctional protein with a protease-independent role in magnetosome protein localization and a protease-dependent role in maturation of small magnetite crystals. Together these results imply the existence of a previously unrecognized “checkpoint” in biomineralization where MamE moderates the completion of magnetite formation and thus committal to magneto-aerotaxis as the organism’s dominant mode of navigating the environment.
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影响因子：
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