Effects of gamma irradiation on the function and conformation of ribonuclease A in dilute solution
Bovine pancreatic ribonuclease A (EC 2.7.7.16) in aqueous solutions has been exposed to gamma irradiation, and several properties of the irradiated enzyme molecule were examined. Kinetic and thermodynamic parameters of RNase A were not affected even when the enzymatic activity was considerably lost by gamma irradiation. While the structural changes of the irradiated RNase A were detected, STAm'!/sub 233/ values gradually decreased with increasing dose. The accessibility of tyrosyl and histidyl residues in the enzyme molecule for a chemical reagent was greatly increased in relatively lower dose ranges. All six tyrosyl residues were diazotized with DHT when 70% of enzymatic activity was still retained. 2'-Cytidilate-binding capacity and enzymatic activity of RNase A were reduced depending on the increase of dose at somewhat different rates. Decrease of the heat of denaturation also indicates that the local conformation change of thc enzymes through gamma irradiation precedes the disappearance of the enzymatic activity. (auth)
- Research Organization:
- Kyoto Univ.
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-29-024052
- OSTI ID:
- 4333716
- Journal Information:
- Radiat. Res., v. 57, no. 2, pp. 349-357, Journal Name: Radiat. Res., v. 57, no. 2, pp. 349-357; ISSN RAREA
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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