Inactivation during denaturation of ribonuclease A by guanidinium chloride is accompanied by unfolding at the active site.
Inactivation of pancreatic RNAase A occurs in guanidinium chloride (GdmCl) at low concentrations before the unfolding of the molecule as a whole can be detected [Liu and Tsou (1987) Biochim. Biophys. Acta 916, 455-464]. We have now shown that the rate of digestion of the RNAase molecule by either trypsin or proteinase K increases significantly at low concentrations of GdmCl where the enzyme is largely inactivated, but fluorescence and absorption measurements reveal no conformational changes. N-Terminal sequence analysis of the peptide fragments generated shows that proteolysis occurs primarily at or near the active site. The decrease in activity of RNAase at low concentrations of GdmCl is therefore due to partial unfolding of the molecule, particularly at the active site and not to an inhibition by the denaturant.
National Laboratory of Biomacromolecules, Institute of Biophysics, Academia Sinica, Beijing, China.
H J
HJ
Yang
C L
CL
Tsou
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D019286:Endopeptidase K; D019791:Guanidine; D006146:Guanidines / Q000494:pharmacology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D012259:Ribonuclease, Pancreatic / Q000737:chemistry* / Q000187:drug effects; D017421:Sequence Analysis; D012697:Serine Endopeptidases / Q000494:pharmacology; D014357:Trypsin / Q000494:pharmacology
D006146:Guanidines; D010446:Peptide Fragments; D012259:Ribonuclease, Pancreatic; D012697:Serine Endopeptidases; D014357:Trypsin; D019286:Endopeptidase K; D019791:Guanidine