3eip
CRYSTAL STRUCTURE OF COLICIN E3 IMMUNITY PROTEIN: AN INHIBITOR TO A RIBOSOME-INACTIVATING RNASE
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OverviewOverview
BACKGROUND: Colicins are antibiotic-like proteins of Escherichia coli that, 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 A. The, structure consists of a four-standard antiparallel beta sheet flanked by, three alpha helices 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.
About this StructureAbout this Structure
3EIP is a Single protein structure of sequence from Escherichia coli with ZN as ligand. Full crystallographic information is available from OCA.
ReferenceReference
Crystal structure of colicin E3 immunity protein: an inhibitor of a ribosome-inactivating RNase., Li C, Zhao D, Djebli A, Shoham M, Structure. 1999 Nov 15;7(11):1365-72. PMID:10574790
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