Crystal structure of colicin E3 immunity protein: an inhibitor of a ribosome-inactivating RNase.
Crystal structure of colicin E3 immunity protein: an inhibitor of a ribosome-inactivating RNase.
复制标题
大肠杆菌素 E3 免疫蛋白的晶体结构：核糖体失活 RNase 的抑制剂。
DOI：
10.1016/s0969-2126(00)80026-x
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发表时间：
1999
期刊：
影响因子：
--
通讯作者：
Shoham,M
中科院分区：
文献类型：
--
作者：
Li,C;Zhao,D;Djebli,A;Shoham,M
Background:Colicins are antibiotic-like proteins ofEscherichia colithat kill related strains. Colicin E3 acts as an RNase that specifically cleaves 16S rRNA, thereby inactivating the ribosomes in the infected cell. The producing organism is protected against colicin E3 by a specific inhibitor, the immunity protein Im3, which forms a tight 1:1 complex with colicin E3 and renders it inactive. Crystallographic studies on colicin E3 and Im3 have been undertaken to unravel the structural basis for the ribonucleolytic activity and its inhibition.Results:The crystal structure of Im3 has been determined to a resolution of 1.8 Å. The structure consists of a four-standard antiparallelβsheet flanked by threeαhelices on one side of the sheet. Thr7, Phe9, Phe16 and Phe74 form a hydrophobic cluster on the surface of the protein in the vicinity of Cys47. This cluster is part of a putative binding pocket which also includes nine polar residues.Conclusions:The putative binding pocket of Im3 is the probable site of interaction with colicin E3. The six acidic residues in the pocket may interact with some of the numerous basic residues of colicin E3. The involvement of hydrophobic moieties in the binding is consistent with the observation that the tight complex can only be dissociated by denaturation. The structure of Im3 resembles those of certain nucleic acid binding proteins, in particular domain II of topoisomerase I and RNA-binding proteins that contain the ribonucleoprotein (RNP) sequence motif. This observation suggests that Im3 has a nucleic acid binding function in addition to binding colicin E3.
