Sturms Ryan, Streauslin Nicholas A, Cheng Shouqiang, Bobik Thomas A
Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, Iowa, USA.
Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, Iowa, USA
J Bacteriol. 2015 Jul;197(14):2412-21. doi: 10.1128/JB.00215-15. Epub 2015 May 11.
Bacterial microcompartments (MCPs) are a diverse family of protein-based organelles composed of metabolic enzymes encapsulated within a protein shell. The function of bacterial MCPs is to optimize metabolic pathways by confining toxic and/or volatile metabolic intermediates. About 20% of bacteria produce MCPs, and there are at least seven different types. Different MCPs vary in their encapsulated enzymes, but all have outer shells composed of highly conserved proteins containing bacterial microcompartment domains. Many organisms have genes encoding more than one type of MCP, but given the high homology among shell proteins, it is uncertain whether multiple MCPs can be functionally expressed in the same cell at the same time. In these studies, we examine the regulation of the 1,2-propanediol (1,2-PD) utilization (Pdu) and ethanolamine utilization (Eut) MCPs in Salmonella. Studies showed that 1,2-PD (shown to induce the Pdu MCP) represses transcription of the Eut MCP and that the PocR regulatory protein is required. The results indicate that repression of the Eut MCP by 1,2-PD is needed to prevent detrimental mixing of shell proteins from the Eut and Pdu MCPs. Coexpression of both MCPs impaired the function of the Pdu MCP and resulted in the formation of hybrid MCPs composed of Eut and Pdu MCP components. We also show that plasmid-based expression of individual shell proteins from the Eut MCP or the β-carboxysome impaired the function of Pdu MCP. Thus, the high conservation among bacterial microcompartment (BMC) domain shell proteins is problematic for coexpression of the Eut and Pdu MCPs and perhaps other MCPs as well.
Bacterial MCPs are encoded by nearly 20% of bacterial genomes, and almost 40% of those genomes contain multiple MCP gene clusters. In this study, we examine how the regulation of two different MCP systems (Eut and Pdu) is integrated in Salmonella. Our findings indicate that 1,2-PD (shown to induce the Pdu MCP) represses the Eut MCP to prevent detrimental mixing of Eut and Pdu shell proteins. These findings suggest that numerous organisms which produce more than one type of MCP likely need some mechanism to prevent aberrant shell protein interactions.
细菌微区室（MCPs）是一类多样的基于蛋白质的细胞器，由包裹在蛋白质外壳内的代谢酶组成。细菌MCPs的功能是通过限制有毒和/或挥发性代谢中间产物来优化代谢途径。约20%的细菌会产生MCPs，且至少有七种不同类型。不同的MCPs所含的包裹酶不同，但它们的外壳均由含有细菌微区室结构域的高度保守蛋白质组成。许多生物体都有编码不止一种类型MCP的基因，但鉴于外壳蛋白之间的高度同源性，尚不确定多种MCPs能否在同一细胞中同时功能性表达。在这些研究中，我们研究了沙门氏菌中1,2 - 丙二醇（1,2 - PD）利用（Pdu）和乙醇胺利用（Eut）MCPs的调控情况。研究表明，1,2 - PD（已证明可诱导Pdu MCP）会抑制Eut MCP的转录，且需要PocR调控蛋白。结果表明，1,2 - PD对Eut MCP的抑制作用是为了防止Eut和Pdu MCP的外壳蛋白发生有害混合。两种MCPs的共表达会损害Pdu MCP的功能，并导致由Eut和Pdu MCP成分组成的杂交MCPs的形成。我们还表明，基于质粒表达来自Eut MCP或β - 羧酶体的单个外壳蛋白会损害Pdu MCP的功能。因此，细菌微区室（BMC）结构域外壳蛋白之间的高度保守性对于Eut和Pdu MCPs以及可能其他MCPs的共表达来说是个问题。
细菌MCPs由近20%的细菌基因组编码，且这些基因组中近40%包含多个MCP基因簇。在本研究中，我们研究了沙门氏菌中两种不同的MCP系统（Eut和Pdu）的调控是如何整合的。我们的研究结果表明，1,2 - PD（已证明可诱导Pdu MCP）会抑制Eut MCP，以防止Eut和Pdu外壳蛋白发生有害混合。这些发现表明，许多产生不止一种类型MCP的生物体可能需要某种机制来防止异常的外壳蛋白相互作用。
