Ribonuclease T1

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Ribonuclease T1 (sometimes abbreviated RNase T1) is a fungal endonuclease that cleaves single-stranded RNA after guanine residues, i.e., on their 3' end; the most commonly studied form of this enzyme is the version found in the mold Aspergillus oryzae. Owing to its specificity for guanine, RNase T1 is often used to digest denatured RNA prior to sequencing. Similar to other ribonucleases such as barnase and RNase A, ribonuclease T1 has been popular for folding studies.[1]

Structurally, ribonuclease T1 is a small α+β protein (104 amino acids) with a four-stranded, antiparallel beta sheet covering a long alpha helix (almost five turns). RNase T1 has two disulfide bonds, Cys2-Cys10 and Cys6-Cys103, of which the latter contributes more to its folding stability;[2] complete reduction of both disulfides usually unfolds the protein, although its folding can be rescued with high salt concentrations.[3]

RNase T1 also has four prolines, two of which (Pro39 and Pro55) have cis isomers of their X-Pro peptide bonds. Nonnative isomers of these prolines can retard conformational folding dramatically,[4] folding on a characteristic time scale of 7,000 seconds (almost two hours) at 10°C and pH 5.[5]

[edit] References

  1. ^ Pace, CN; Heinemann U, Hahn U, Saenger W (1991). "Ribonuclease T1: Structure, Function, and Stability". Angewandte Cheni, International Edition 30: 343–360. doi:10.1002/anie.199103433. 
  2. ^ Pace, CN; Grimsley GR, Thomson JA, Barnett BJ (1988). "Conformational stability and activity of ribonuclease T1 with zero, one, and two intact disulfide bonds". Journal of Biological Chemistry 263: 11820–11825. 
  3. ^ Oobatake, M; Takahashi S, Ooi T (1979). "Conformational stability of ribonuclease T1. II. Salt-induced renaturation". Journal of Biochemistry (Tokyo) 86: 65–70. 
  4. ^ Mayr, LM; Odefey CO, Schutkowski M, Schmid FX (1996). "Kinetic analysis of the unfolding and refolding of ribonuclease T1 by a stopped-flow double-mixing technique". Biochemistry 35: 5550–5561. doi:10.1021/bi953035y. 
  5. ^ Mullins, LS; Pace CN and Raushel FM (1997). "Conformational stability of ribonuclease T1 measured by hydrogen-deuterium exchange". Protein Science 6: 1387–1395. 

[edit] External links

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Hydrolase, esterase: nucleases (EC 3.1.11 - 3.1.31) - includes deoxyribonuclease and ribonuclease
3.1.11-16: Exonuclease
3.1.21-31: Endonuclease