This old version of Proteopedia is provided for student assignments while the new version is undergoing repairs. Content and edits done in this old version of Proteopedia after March 1, 2026 will eventually be lost when it is retired in about June of 2026.
Apply for new accounts at the new Proteopedia. Your logins will work in both the old and new versions.
1v1d
From Proteopedia
| |||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||
NUCLEOPHILIC AND GENERAL ACID CATALYSIS AT PHYSIOLOGICAL PH BY A DESIGNED MINIATURE ESTERASE
Overview
A 31-residue peptide (Art-Est) was designed to catalyse the hydrolysis of p-nitrophenyl esters through histidine catalysis on the solvent exposed face of the alpha-helix of bovine pancreatic polypeptide. NMR spectroscopy indicated that Art-Est adopted a stable 3-dimensional structure in solution. Art-Est was an efficient catalyst with second order rate constants of up to 0.050 M(-1) s(-1). The activity of Art-Est was a consequence of the increased nucleophilicity of His-22, which had a reduced pK(a) value of 5.5 as a consequence of its interaction with His-18 and the positively charged Arg-25 and Arg-26. Mass spectrometry and NMR spectroscopy confirmed that the Art-Est catalysed hydrolysis of p-nitrophenyl esters proceeded through an acyl-enzyme intermediate. A solvent kinetic isotope effect of 1.8 indicated that the transition state preceding the acyl intermediate was stabilised through interaction with the protonated side-chain of His-18 and indicated a reaction mechanism similar to that generally observed for natural esterases. The involvement in the reaction of two histidine residues with different pK(a) values led to a bell-shaped dependence of the reaction rate on the pH of the solution. The catalytic behaviour of Art-Est indicated that designed miniature enzymes can act in a transparent mechanism based fashion with enzyme-like behaviour through the interplay of several amino acid residues.
About this Structure
1V1D is a Single protein structure of sequence from [1]. Full crystallographic information is available from OCA.
Reference
Nucleophilic and general acid catalysis at physiological pH by a designed miniature esterase., Nicoll AJ, Allemann RK, Org Biomol Chem. 2004 Aug 7;2(15):2175-80. Epub 2004 Jul 8. PMID:15280952
Page seeded by OCA on Thu Mar 20 14:39:37 2008
