Using a biomimetic membrane surface experiment to investigate the activity of the magnetite biomineralisation protein Mms6.
Using a biomimetic membrane surface experiment to investigate the activity of the magnetite biomineralisation protein Mms6.
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DOI：
10.1039/c5ra16469a
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发表时间：
2016-01-29
期刊：
影响因子：
3.9
通讯作者：
Staniland SS
中科院分区：
文献类型：
--
作者：
Bird SM;Rawlings AE;Galloway JM;Staniland SS
使用磁小体内部的基于表面的模拟物，发现生物矿化蛋白Mms 6是比磁铁矿纳米颗粒的粘合剂更有效的成核剂，并且比单独的C-末端区域表现更好。趋磁细菌能够在其细胞内合成氧化铁磁铁矿的精确纳米颗粒。这些颗粒形成于称为磁小体的专用细胞器中。这些脂质膜隔室使用一系列生物矿化蛋白质来成核和调节磁铁矿结晶过程。一个关键的组成部分是膜蛋白Mms 6，它与铁离子结合，有助于控制无机核心的形成。我们以前使用Mms 6在金表面图案化的自组装单层，成功地产生阵列的磁性纳米粒子。在这里，我们使用这个表面系统作为模拟的磁小体膜的内表面，研究完整的Mms 6和富含酸的C-末端肽亚区的Mms 6蛋白之间的差异。当固定在表面上时，肽不能再现在我们的实验装置中由完整Mms 6蛋白质所表现出的颗粒大小或均匀性对照。此外，肽不能支持纳米颗粒的密集阵列锚定到表面。该系统还允许我们从颗粒成核中去卷积颗粒结合，并且表明当与在表面固定化的Mms 6的存在下从溶液中沉淀的颗粒相比时，Mms 6颗粒结合在提供有预先形成的磁铁矿纳米颗粒时效率较低。这表明，Mms 6结合到铁离子，而不是磁铁矿表面在我们的系统中，可能是一个成核剂，而不是磁铁矿晶体生长的控制器。在相同的实验条件下肽和蛋白质之间的比较表明，需要全长序列来支持Mms 6在表面上的全部功能。
Using a surface-based mimic of a magnetosome interior, the biomineralisation protein Mms6 was found to be a more effective nucleator than binder of magnetite nanoparticles, and performs better than its C-terminal region alone. Magnetotactic bacteria are able to synthesise precise nanoparticles of the iron oxide magnetite within their cells. These particles are formed in dedicated organelles termed magnetosomes. These lipid membrane compartments use a range of biomineralisation proteins to nucleate and regulate the magnetite crystallisation process. A key component is the membrane protein Mms6, which binds to iron ions and helps to control the formation of the inorganic core. We have previously used Mms6 on gold surfaces patterned with a self-assembled monolayer to successfully produce arrays of magnetic nanoparticles. Here we use this surface system as a mimic of the interior face of the magnetosome membrane to study differences between intact Mms6 and the acid-rich C-terminal peptide subregion of the Mms6 protein. When immobilised on surfaces, the peptide is unable to reproduce the particle size or homogeneity control exhibited by the full Mms6 protein in our experimental setup. Moreover, the peptide is unable to support anchoring of a dense array of nanoparticles to the surface. This system also allows us to deconvolute particle binding from particle nucleation, and shows that Mms6 particle binding is less efficient when supplied with preformed magnetite nanoparticles when compared to particles precipitated from solution in the presence of the surface immobilised Mms6. This suggests that Mms6 binds to iron ions rather than to magnetite surfaces in our system, and is perhaps a nucleating agent rather than a controller of magnetite crystal growth. The comparison between the peptide and the protein under identical experimental conditions indicates that the full length sequence is required to support the full function of Mms6 on surfaces.