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Title: Characterisation of the N-terminal domain of eukaryotic ribonuclease HI
Author: Evans, S. P.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2001
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In addition to the conserved and well-defined RNase H domain, eukaryotic RNases HI possess either one or two copies of a small N-terminal domain. The solution structure of one of the N-terminal domains from S. cerevisiae RNase HI, determined using NMR spectroscopy, is presented. The 46 residue motif comprises a three-stranded antiparallel β-sheet and two short α-helices which pack onto opposite faces of the β-sheet. Conserved residues involved in packing the α-helices onto the β-sheet form the hydrophobic core of the domain. The structure shows that the RNase HI N-terminal domain is not related to the double-stranded RNA binding domain (dsRBD) as had been previously suggested. The β-β-α-β-α topology of the domain also differs from the structures of other recognised RNA binding domains, such as the hnRNP K homology (KH) domain, the RNP motif and the S1/cold shock domain. NMR chemical shift mapping and isothermal titration calorimetry confirm that the RNase HI N-terminal domain binds dsRNA. Three highly conserved and solvent exposed residues, W22, K38 and K39, are implicated in a non-sequence specific mode of RNA binding. Finally, a potential evolutionary relationship with the N-terminal domain of Ribosomal Protein L9, known to bind 23S rRNA, is identified. The two domains are shown to exhibit strong structural similarities as well as some common biophysical properties. In conclusion these studies reveal that the RNase HI N-terminal domain forms a novel motif for recognition of dsRNA, and suggest that the domain may have ribosomal origin.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available