Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.26.9 (ribonuclease)
 6,589 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Colicin E5 is a tRNA-specific ribonuclease that recognizes and cleaves four tRNAs in Escherichia coli that contain the hypermodified nucleoside queuosine (Q) at the wobble position. Cells that produce colicin E5 also synthesize the cognate immunity protein (Im5) that rapidly and tightly associates with colicin E5 to prevent it from cleaving its own tRNAs to avoid suicide. We report here the crystal structure of Im5 in a complex with the activity domain of colicin E5 (E5-CRD) at 1.15A resolution. The structure reveals an extruded domain from Im5 that docks into the recessed RNA binding cleft in E5-CRD, resulting in extensive interactions between the two proteins. The interactions are primarily hydrophilic, with an interface that contains complementary surface charges between the two proteins. Detailed interactions in three separate regions of the interface account for specific recognition of colicin E5 by Im5. Furthermore, single-site mutational studies of Im5 confirmed the important role of particular residues in recognition and binding of colicin E5. Structural comparison of the complex reported here with E5-CRD alone, as well as with a docking model of RNA-E5-CRD, indicates that Im5 achieves its inhibition by physically blocking the cleft in colicin E5 that engages the RNA substrate.
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PMID:Molecular basis of inhibition of the ribonuclease activity in colicin E5 by its cognate immunity protein. 1652 91

Colicin E5 is a ribonuclease that specifically cleaves tRNA(Tyr), tRNA(His), tRNA(Asn) and tRNA(Asp) of sensitive Escherichia coli cells by recognizing their anticodon sequences. Since all organisms possess universal anticodons of these tRNAs, colicin E5 was expected to potentially cleave eukaryotic tRNAs. Here, we expressed the active domain of colicin E5 (E5-CRD) in Saccharomyces cerevisiae and investigated its effects on growth. E5-CRD impaired growth of host cells by cleaving tRNA(Tyr), tRNA(His), tRNA(Asn) and tRNA(Asp) in S. cerevisiae, which is the same repertoire as that in E. coli. This activity of E5-CRD was inhibited by the co-expression of its cognate inhibitor (ImmE5). Notably, the growth impairment by E5-CRD was reversible; cells restored the colony-forming activity after suppression of the E5-CRD expression. This seems different from the sharp killing effect of E5-CRD on E. coli. These results may provide insights into the role and behaviour of cytosolic tRNAs on cell growth and proliferation.
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PMID:Colicin E5 ribonuclease domain cleaves Saccharomyces cerevisiae tRNAs leading to impairment of the cell growth. 1915 Nov 2