THE CHAPERONE CATALYST FULL

However, an additional mutation in the propeptide substituting Glu-2 with His was able to suppress the His64Ala mutation, allowing autoprocessing of the propeptide. This mechanism is blocked when His64, a member of the catalytic triad is substituted with Ala. After folding, the propeptide is removed via an intramolecular autoprocessing mechanism. This suppression is considered to be due to a 'substrate assisted catalysis' mechanism and demonstrates that the cleavage to the subtilisin propeptide is an autocatalytic process.ĪB - Subtilisin is synthesized with an N-terminal propeptide which has been demonstrated to function as an intramolecular chaperone that is only essential for the folding of the active enzyme. N2 - Subtilisin is synthesized with an N-terminal propeptide which has been demonstrated to function as an intramolecular chaperone that is only essential for the folding of the active enzyme. and the National Science Foundation grant number MCB 9105293. The present work is partially supported by a grant from Ajinomoto Co. N1 - Funding Information: We thank Dr Ann Stock and Dr Barbara Brodsky, Dr Parkash Badola and Jan Yadav for their helpful discussions during this entire work. T2 - Autoprocessing pathway of the precursor resolved via a substrate assisted catalysis mechanism the chaperone property, of the intact trigger factor is responsible for its high efficiency as a catalyst of proline‐limited protein folding.T1 - Folding mediated by an intramolecular chaperone Together, this suggests that the good substrate binding, i.e. Unlike the prolyl isomerase site, the polypeptide binding site obviously extends beyond the FKBP domain.

THE CHAPERONE CATALYST FULL

The isolated catalytic domain of the trigger factor retains the full prolyl isomerase activity towards short peptides, but in a protein folding reaction its activity is 800‐fold reduced and no longer inhibited by an unfolded protein. An unfolded protein inhibits the trigger factor in a competitive fashion. Recent studies suggest that these two chaperone/catalysts exploit structural flexibility and dynamics to stabilize MHC molecules and facilitate peptide loading. In contrast, the catalytic constant kcat is small and shows a value of 1.3 s−1 at 15☌. Regions of structural conservation among species suggest that TAPBPR and tapasin have evolved to satisfy functional complexities demanded by the enormous polymorphism of MHC I molecules. The unusually high folding activity of the trigger factor originates from its tight binding to the folding protein substrate, as reflected in the low Km value of 0.7 μM. In its enzymatic mechanism the trigger factor follows the Michaelis–Menten equation. It associates with nascent polypeptide chains at the ribosome and is thought to catalyse the folding of newly synthesized proteins. The trigger factor of Escherichia coli is a prolyl isomerase and accelerates proline‐limited steps in protein folding with a very high efficiency. Scholz, Christian Stoller, Gerlind Zarnt, Toralf Fischer, Gunter Schmid, Franz X. Cooperation of enzymatic and chaperone functions of trigger factor in the catalysis of protein folding Cooperation of enzymatic and chaperone functions of trigger factor in the catalysis of protein.

The chaperone catalyst