Modulating protein structure with fluorous amino acids: increased stability and native-like structure conferred on a 4-helix bundle protein by hexafluoroleucine.

Published

Journal Article

There has recently been much interest in exploiting the unusual properties associated with fluorocarbons to modulate the physicochemical properties of proteins. Here we present a detailed investigation into the effect on structure and stability of systematically repacking the hydrophobic core of a model protein with the extensively fluorinated (fluorous) amino acid l-5,5,5,5',5',5'-hexafluoroleucine (hFLeu). The starting point was a 27-residue peptide, alpha(4)-H, that adopts an antiparallel 4-alpha-helix bundle structure, and in which the hydrophobic core comprises six layers of leucine residues introduced at the "a" and "d" positions of the canonical heptad repeat. A series of peptides were synthesized in which the central two (alpha(4)-F(2))(,) four (alpha(4)-F(4)), or all six layers (alpha(4)-F(6)) of the core were substituted hFLeu. The free energy of unfolding increases by 0.3 (kcal/mol)/hFLeu on repacking the central two layers and by an additional 0.12 (kcal/mol)/hFLeu on repacking additional layers, so that alpha(4)-F(6) is approximately 25% more stable than the nonfluorinated protein alpha(4)-H. One-dimensional proton, two-dimensional (1)H-(15)N HSQC, and (19)F NMR spectroscopies were used to examine the effect of fluorination on the conformational dynamics of the peptide. Unexpectedly, increasing the degree of fluorination also appears to result in peptides that possess a more structured backbone and less fluid hydrophobic core. The latter only occurs in alpha(4)-F(4) and alpha(4)-F(6), suggesting that crowding of the hFLeu residues may restrict the amplitude and/or time scales for rotation of the side chains.

Full Text

Duke Authors

Cited Authors

  • Lee, H-Y; Lee, K-H; Al-Hashimi, HM; Marsh, ENG

Published Date

  • January 11, 2006

Published In

Volume / Issue

  • 128 / 1

Start / End Page

  • 337 - 343

PubMed ID

  • 16390163

Pubmed Central ID

  • 16390163

International Standard Serial Number (ISSN)

  • 0002-7863

Digital Object Identifier (DOI)

  • 10.1021/ja0563410

Language

  • eng

Conference Location

  • United States