Peptide hydrogen exchange rates in Streptomyces subtilisin inhibitor.
The exchange reaction of the peptide NH protons of a microbial protease inhibitor (Streptomyces subtilisin inhibitor) with deuterium atoms in 2H2O (p2H 6.8) has been studied by proton magnetic resonance in the temperature range 56-71 degrees C. Both slowly and rapidly exchanging processes have been observed. The number of slowly exchanging protons is estimated to be 25 +/- 2 per subunit of the protein molecule. The decay of the slowly exchanging proton signals follows a single time-exponential function at each temperature. The observed first-order rate constants have been analyzed to give the denaturated fraction of the protein as a function of temperature with a consequent enthalpy (56 kcal/mol) and an entropy (137 cal/degree per mol) of denaturation. The results indicate the high conformational stability of this protein against heat denaturation.
D001426:Bacterial Proteins / Q000032:analysis / Q000494:pharmacology; D001665:Binding Sites; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008433:Mathematics; D011485:Protein Binding; D011487:Protein Conformation; D011489:Protein Denaturation; D013302:Streptomyces / Q000032:analysis*; D013381:Subtilisins / Q000037:antagonists & inhibitors*; D013696:Temperature
D001426:Bacterial Proteins; D013381:Subtilisins