Interactions between the termini of lumen enzymes and shell proteins mediate enzyme encapsulation into bacterial microcompartments
Interactions between the termini of lumen enzymes and shell proteins mediate enzyme encapsulation into bacterial microcompartments
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DOI：
10.1073/pnas.1207516109
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发表时间：
2012-09-11
影响因子：
11.1
通讯作者：
Bobik, Thomas A.
中科院分区：
文献类型：
--
作者：
Fan, Chenguang;Cheng, Shouqiang;Bobik, Thomas A.
细菌微区室（MCP）是一个广泛分布的蛋白质细胞器家族，由包封在蛋白质壳内的代谢酶组成。要使MCP发挥功能，必须将特定的酶包封起来。我们最近报道，一个短的N-末端的丙醛脱氢酶（PduP）的靶向序列是必要的，足够的包装成MCP的功能，在1，2-丙二醇（1，2-PD）利用（Pdu）的肠道沙门氏菌的酶。在这里，我们表明，封装介导的结合的PduP靶向序列的短C-末端螺旋的PduA壳蛋白。体外研究表明PduP和PduA（和PduJ）之间的结合，但不是其他MCP壳蛋白。丙氨酸扫描诱变确定参与结合的关键残基是PduP的E7、I10和L14以及PduA的H81、V84和L 88。体内靶向研究表明，PduP的N末端和PduA的C末端之间的结合对于PduP在Pdu MCP内的包封是至关重要的。结构模型表明PduP的N端和PduA的C端都形成螺旋结构，通过诱变鉴定的关键残基相互结合。累积地，这些结果表明PduP的N-末端靶向序列通过结合MCP壳蛋白促进其包封。这是确定MCP靶向序列功能的机制的独特报告。我们建议，特定的壳蛋白和管腔酶的末端之间的相互作用具有指导的组装和细菌MCP的更高层次的组织的一般重要性。
Bacterial microcompartments (MCPs) are a widespread family of proteinaceous organelles that consist of metabolic enzymes encapsulated within a protein shell. ForMCPs to function specific enzymes must be encapsulated. We recently reported that a short N-terminal targeting sequence of propionaldehyde dehydrogenase (PduP) is necessary and sufficient for the packaging of enzymes into a MCP that functions in 1,2-propanediol (1,2-PD) utilization (Pdu) by Salmonella enterica. Here we show that encapsulation is mediated by binding of the PduP targeting sequence to a short C-terminal helix of the PduA shell protein. In vitro studies indicated binding between PduP and PduA (and PduJ) but not other MCP shell proteins. Alanine scanning mutagenesis determined that the key residues involved in binding are E7, I10, and L14 of PduP and H81, V84, and L88 of PduA. In vivo targeting studies indicated that the binding between the N terminus of PduP and the C terminus of PduA is critical for encapsulation of PduP within the Pdu MCP. Structural models suggest that the N terminus of PduP and C terminus of PduA both form helical structures that bind one another via the key residues identified by mutagenesis. Cumulatively, these results show that the N-terminal targeting sequence of PduP promotes its encapsulation by binding to MCP shell proteins. This is a unique report determining the mechanism by which a MCP targeting sequence functions. We propose that specific interactions between the termini of shell proteins and lumen enzymes have general importance for guiding the assembly and the higher level organization of bacterial MCPs.