β Scribed by Lars Baltzer; Kerstin S. Broo
No coin nor oath required. For personal study only.
Designed polypeptide catalysts have been shown to catalyze hydrolysis and transesterification reactions of p-nitrophenyl esters by a mechanism that includes the nucleophilic attack by an unprotonated histidine and general-acid catalysis by a flanking protonated histidine. The catalysis is cooperative and exhibits rate enhancements of three orders of magnitude over that of the 4-methylimidazole catalyzed reaction. Substrate recognition by residues introduced in the adjoining helix was demonstrated for the negatively charged substrate mono-pnitrophenyl fumarate. The results have been compared to those obtained for other designed polypeptide catalysts with similar efficiency, and it was concluded that the hallmarks of naturally occurring biocatalysts have now been demonstrated in polypeptide catalyzed reactions, although with considerably less efficiency than native enzymes. It was found that so far the most severe limitation of folded polypeptide catalysts is the efficiency obtained in the bondmaking and bond-breaking steps, whereas the binding of substrates, even on the surface of helical structures in aqueous solution, is of comparable strength to that which occurs in nature.
π SIMILAR VOLUMES
## Abstract Stereochemistry could be a powerful variable for conformational tune up of polypeptides for de novo design. It may be also useful probe of possible role of interamide energetics in selection and stabilization of conformation. The homopolypeptides AcβXxx~30~βNHMe, with Xxx = Ala, Val, an
The solution to the protein folding problem lies in defining the relative energetic contributions of short-range and long-range interactions. In other words, the tendency of a stretch of amino acids to adopt a final secondary structural fold is context dependent. Our approach to this problem is to a