Department of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, Farmington, Connecticut 06032, USA.
J Biol Chem. 2013 Mar 8;288(10):7241-51. doi: 10.1074/jbc.M112.408674. Epub 2013 Jan 23.
The subcellular localization of the exoribonuclease RNase II is not known despite the advanced biochemical characterization of the enzyme. Here we report that RNase II is organized into cellular structures that appear to coil around the Escherichia coli cell periphery and that RNase II is associated with the cytoplasmic membrane by its amino-terminal amphipathic helix. The helix also acts as an autonomous transplantable membrane binding domain capable of directing normally cytoplasmic proteins to the membrane. Assembly of the organized cellular structures of RNase II required the RNase II amphipathic membrane binding domain. Co-immunoprecipitation of the protein from cell extracts indicated that RNase II interacts with itself. The RNase II self-interaction and the ability of the protein to assemble into organized cellular structures required the membrane binding domain. The ability of RNase II to maintain cell viability in the absence of the exoribonuclease polynucleotide phosphorylase was markedly diminished when the RNase II cellular structures were lost due to changes in the amphipathicity of the amino-terminal helix, suggesting that membrane association and assembly of RNase II into organized cellular structures play an important role in the normal function of the protein within the bacterial cell.
尽管已经对该酶进行了先进的生化特性分析，但核糖核酸外切酶 RNase II 的亚细胞定位仍不清楚。本文报道称，RNase II 形成了细胞结构，这些结构似乎围绕着大肠杆菌细胞外周盘旋，并且 RNase II 通过其氨基末端的两亲性螺旋与细胞质膜结合。该螺旋还充当自主可移植的膜结合结构域，能够将通常位于细胞质中的蛋白质引导至膜上。RNase II 有组织的细胞结构的组装需要 RNase II 的两亲性膜结合结构域。从细胞提取物中进行的共免疫沉淀表明，RNase II 与自身相互作用。RNase II 的自我相互作用以及该蛋白组装成有组织的细胞结构的能力需要膜结合结构域。当由于氨基末端螺旋的两亲性变化而导致 RNase II 的细胞结构丢失时，RNase II 维持细胞活力的能力明显降低，这表明膜结合和将 RNase II 组装成有组织的细胞结构在该蛋白在细菌细胞内的正常功能中起着重要作用。
