Cured of “Stickiness”, Poly-l β-Hairpin is Promoted with ll-to-dd Mutation as a Protein an
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- 作者：Kirti Patel ; Bhupesh Goyal ; Anil Kumar ; Nand Kishore ; Susheel Durani
- 刊名：Journal of Physical Chemistry B
- 出版年：2010
- 出版时间：December 23, 2010
- 年：2010
- 卷：114
- 期：50
- 页码：16887-16893
- 全文大小：228K
- 年卷期：v.114,no.50(December 23, 2010)
- ISSN：1520-5207
文摘
The planar ribbon of the poly-l β-hairpin is modified to a local 90° bend by mutating a cross-strand pair of residues from ll to dd structure. The bend is furnished aromatic side chains in proximity of acid−base−nucleophile side chains, toward the possibility of catalyzed hydrolysis of an active-site-anchored substrate. Six sequences permuted in putative catalytic side chains are evaluated for activity and variability as hydrolase enzymes. Studies using CD, NMR, spectorofluorometry, ITC, and molecular dynamics establish that the sequences over the bent β-hairpin are by and large aggregation-free folds soluble to at least millimolar concentration, and thus remarkably contrasted with “stickiness” of the canonical poly-l β-hairpin. The heterochiral fold displays cooperative ordering and affinity for acetylcholine, p-nitrophenylacetate, and p-nitrophenylphosphate, presumably as the ligands in its aromatic pocket as a bent hairpin. The fold displays hydrolytic activity against p-nitrophenylacetate and manifests saturation kinetics with respect to substrate concentration. However, the catalysis power is feeble, which remains unaffected by repositioning acid−base−nucleophile side chains. Stereochemistry is proven to be critical in the balance between mutually competitive forces of polypeptide structure involved in guidance of folding or aggregation of the structure. Residue stereochemistry is confirmed in its value as the alphabet for design of protein folds to desired molecular shapes.