Mechanism of folding and conformational stability of ribonuclease T1 /
| Main Author: | |
|---|---|
| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1990.
|
| Subjects: | |
| Online Access: | ProQuest, Abstract Link to OAKTrust copy |
| Abstract: | Urea and thermal unfolding curves for ribonuclease T1 (RNase T1) were determined by measuring several different physical properties. In all cases, steep, single-step unfolding curves were observed. When these results were analyzed by assuming a two-state folding mechanism, the plots of fraction unfolded protein versus denaturant were coincident. A single kinetic phase was observed for both the folding and unfolding of RNase Tl in the transition and post-transition regions. However, two slow kinetic phases were observed during folding in the pre-transition region. These two slow phases account for about 90% of the observed amplitude, indicating that a faster kinetic phase is also present. The slow phases probably result from cis-trans isomerization at the 2 proline residues that have a cis configuration in the folded RNase Tl. The thermal denaturation of RNase Tl was also studied by means of highly sensitive differential scanning calorimetry. Comparison of the calorimetric enthalpy and van't Hoff enthalpy along with the above results suggest that RNase T1 folds by a highly cooperative mechanism with no structural intermediates once the proline residues have assumed their correct isomeric configuration. The pH dependence of the conformational stability of RNase T1 and RNase A suggests that electrostatic interactions among the charged groups make a relatively small contribution to the stability of these proteins. The dependence of AG on urea concentration varies with pH. The results suggest that the unfolded conformations of these proteins become more accessible to urea as the net charge on the molecules increases. |
|---|---|
| Item Description: | Typescript (photocopy). Vita. "Major subject: Biochemistry." |
| Physical Description: | xiv, 145 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |