Formation of the hydrophobic core of ribonuclease A through sequential coordinated conformational transitions.
With steady-state and time-resolved fluorescence energy-transfer measurements, we determined the distributions of intramolecular distances in nine mutants to study the conformations of wild-type ribonuclease A in the reduced state under folding conditions. Although far-UV-CD measurements show no evidence for a secondary-structure transition, temperature- and GdnHCl-induced changes in intramolecular distance distributions in the reduced state revealed evidence for long-range subdomain structures in the denatured protein. These poorly defined structures, reflected here by wide distributions corresponding to a wide range of energies, form during refolding in a complex sequence of multiple subdomain transitions. A more well-defined structure emerges only when this structural framework, which directs the successive steps in the folding process, matures and is reinforced by stronger interactions such as disulfide bonds.
Navon
Ami
A
Faculty of Life Sciences, Bar Ilan University, Ramat Gan, Israel 52900.
Ittah
Varda
V
Scheraga
Harold A
HA
Haas
Elisha
E
D000818:Animals; D002417:Cattle; D002942:Circular Dichroism; D003080:Cold Temperature; D031541:Fluorescence Resonance Energy Transfer / Q000379:methods; D019791:Guanidine / Q000737:chemistry; D006358:Hot Temperature; D057927:Hydrophobic and Hydrophilic Interactions; D016297:Mutagenesis, Site-Directed; D010084:Oxidation-Reduction; D011487:Protein Conformation; D011489:Protein Denaturation / Q000235:genetics; D017510:Protein Folding; D017434:Protein Structure, Tertiary / Q000235:genetics; D012259:Ribonuclease, Pancreatic / Q000737:chemistry* / Q000235:genetics
D012259:Ribonuclease, Pancreatic; D019791:Guanidine