The C-terminal peptide of Aquifex aeolicus riboflavin synthase directs encapsulation of native and foreign guests by a cage-forming lumazine synthase
The C-terminal peptide of Aquifex aeolicus riboflavin synthase directs encapsulation of native and foreign guests by a cage-forming lumazine synthase
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DOI：
10.1074/jbc.c117.790311
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发表时间：
2017-06-23
影响因子：
4.8
通讯作者：
Hilvert, Donald
中科院分区：
文献类型：
--
作者：
Azuma, Yusuke;Zschoche, Reinhard;Hilvert, Donald
在自组装蛋白笼中封装特定的酶是细菌室的一个标志，其功能与真核细胞器相当。例如，枯草芽孢杆菌（BsLS）的笼形酶lumazine synthase （LS）封装了核黄素合成酶（BsRS），使lumazine从其生成位点转运到其转化为维生素B-2的位点。阐明这些超分子复合物组装的分子机制有助于为代谢工程、纳米技术和药物输送提供新方法。为此，我们研究了一种来自AaLS的耐热LS，发现当这两种蛋白在大肠杆菌的细胞质中共同产生时，它也能与同源核黄素合成酶（AaRS）形成笼状复合物。AaRS的C端有一个12个氨基酸长的肽段，作为一个特定的定位序列，负责将客体靶向到蛋白质区室。序列比较表明，类似的肽段可能在其他细菌物种的LS笼中直接RS络合。该肽标签与异源客体分子的共价融合导致其在体内和体外内化到AaLS组装中，为创建用于医疗和生物技术应用的定制仿生纳米室提供了坚实的基础。
Encapsulation of specific enzymes in self-assembling protein cages is a hallmark of bacterial compartments that function as counterparts to eukaryotic organelles. The cage-forming enzyme lumazine synthase (LS) from Bacillus subtilis (BsLS), for example, encapsulates riboflavin synthase (BsRS), enabling channeling of lumazine from the site of its generation to the site of its conversion to vitamin B-2. Elucidating the molecular mechanisms underlying the assembly of these supramolecular complexes could help inform new approaches for metabolic engineering, nanotechnology, and drug delivery. To that end, we investigated a thermostable LS from Aquifex aeolicus (AaLS) and found that it also forms cage complexes with the cognate riboflavin synthase (AaRS) when both proteins are co-produced in the cytosol of Escherichia coli. A 12-amino acid-long peptide at the C terminus of AaRS serves as a specific localization sequence responsible for targeting the guest to the protein compartment. Sequence comparisons suggested that analogous peptide segments likely direct RS complexation by LS cages in other bacterial species. Covalent fusion of this peptide tag to heterologous guest molecules led to their internalization into AaLS assemblies both in vivo and in vitro, providing a firm foundation for creating tailored biomimetic nanocompartments for medical and biotechnological applications.