Abstract
Partitioning properties of transmembrane (TM) polypeptide segments directly determine membrane protein folding, stability, and function, and their understanding is vital for rational design of membrane active peptides. However, direct determination of water-to-bilayer transfer of TM peptides has proved difficult. Experimentally, sufficiently hydrophobic peptides tend to aggregate, while atomistic computer simulations at physiological temperatures cannot yet reach the long time scales required to capture partitioning. Elevating temperatures to accelerate the dynamics has been avoided, as this was thought to lead to rapid denaturing. However, we show here that model TM peptides (WALP) are exceptionally thermostable. Circular dichroism experiments reveal that the peptides remain inserted into the lipid bilayer and are fully helical, even at 90 °C. At these temperatures, sampling is ∼50-500 times faster, sufficient to directly simulate spontaneous partitioning at atomic resolution. A folded insertion pathway is observed, consistent with three-stage partitioning theory. Elevated temperature simulation ensembles further allow the direct calculation of the insertion kinetics, which is found to be first-order for all systems. Insertion barriers are ΔHin ‡ 15 kcal/mol for a general hydrophobic peptide and ∼23 kcal/mol for the tryptophan-flanked WALP peptides. The corresponding insertion times at room temperature range from 8.5 μS to 163 ms. High-temperature simulations of experimentally validated thermostable systems suggest a new avenue for systematic exploration of peptide partitioning properties. © 2010 American Chemical Society.
| Original language | English |
|---|---|
| Pages (from-to) | 3452-3460 |
| Number of pages | 9 |
| Journal | Journal of the American Chemical Society |
| Volume | 132 |
| Issue number | 10 |
| DOIs | |
| Publication status | Published - 17 Mar 2010 |
Bibliographical note
Cited By (since 1996): 1This book contains a critical edition, with German translation, of a short Latin treatise which the authors call Tractatus de instrumentis artis memorie. It is the third part of the Secretum de thesauro experimentorum ymaginationis hominum by Johannes (or Giovanni) Fontana (ca. 1390--ca. 1455), who was born in Venice and studied in Padua. The text exists in a unique manuscript in Paris, where it is written in a simple code in which each Latin letter is represented by its own symbol. In the Tractatus de instrumentis artis memorie, Fontana describes twelve simple instruments which can be used as memory aids. For each instrument, the manuscript provides a figure which is photographically reproduced in the book under review. For example, Fontana's first instrument is called the speculum (mirror); it consists of five concentric rings which can be rotated around a central axis. On each of the rings, the letters of the alphabet are inscribed in order. Fontana suggests that an arbitrary combination of five letters (such as XROTA) can be remembered by turning the rings such that the letters X, R, O, T, A are on the radius of the instrument from the central axis to the left side.