Mu Gao, David Craig, Viola Vogel, and Klaus Schulten.
Identifying unfolding intermediates of FN-III10 by steered
molecular dynamics.
Journal of Molecular Biology, 323:939-950, 2002.
GAO2002A
Experimental studies have indicated that FN-III
modules undergo reversible unfolding as a
mechanism of elasticity. The unfolding of FN-III
modules, including the cell binding FN-III-10 module,
has further been suggested to be functionally
relevant by exposing buried cryptic sites or modulating
cell binding. While steered molecular dynamics (SMD)
simulations have provided one tool to investigate this
process, computational requirements so far have
limited detailed analysis to the early stages of
unfolding. In this paper we use an extended periodic
box to probe the unfolding of FN-III-10 for extensions
longer than 60 A. Up to three plateaus, corresponding
to three metastable intermediates, were observed in
the extension-time profile from SMD stretching of FN-
III-10. The first and second plateaus correspond to a
twisted and an aligned state prior to unraveling FN-III-
10's beta-strands. The third plateau, at an extension of
100 A, follows unraveling of FN-III's A- and
B-strands and precedes breaking of inter-strand
hydrogen bonds between F- and G-strands. The
simulations revealed three forced unfolding pathways
of FN-III-10, one of which is preferentially selected
under physiological conditions.
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