C. Micheletti, V. De Filippis, A. Maritan and F. Seno
Elucidation of the Disulfide-Folding Pathway of Hirudin by a
Topology-Based Approach
Proteins, 53, 720-730 (2003).
Link to online article.
ABSTRACT
A theoretical model for the folding of proteins containing disulfide
bonds is introduced. The model exploits the knowledge of the native
state to favour the progressive establishment of native
interactions. At variance with traditional approaches based on native
topology, not all native bonds are treated in the same way; in
particular, a suitable energy term is introduced to account for the
special strength of disulfide bonds (irrespective of whether they are
native or not) as well as their ability to undergo intra-molecular
reshuffling. The model thus possesses the minimal ingredients
necessary to investigated the much debated issue of whether the
re-folding process occurs through partially structured intermediates
with native or non-native disulfide bonds. This strategy is applied to
a context of particular interest, the re-folding process of Hirudin, a
thrombin-specific protease inhibitor, for which conflicting folding
pathways have been proposed. We show that the only two parameters in
the model (temperature and disulfide strength) can be tuned to
reproduce well a set of experimental transitions between species with
different number of formed disulfide. This model is then used to
provide a characterisation of the folding process and a detailed
description of the species involved in the rate-limiting step of
Hirudin refolding.