Comparison of the early stages of forced unfolding for fibronectin type III modules

Citation
D. Craig et al., Comparison of the early stages of forced unfolding for fibronectin type III modules, P NAS US, 98(10), 2001, pp. 5590-5595
Citations number
40
Categorie Soggetti
Multidisciplinary
Journal title
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
ISSN journal
00278424 → ACNP
Volume
98
Issue
10
Year of publication
2001
Pages
5590 - 5595
Database
ISI
SICI code
0027-8424(20010508)98:10<5590:COTESO>2.0.ZU;2-R
Abstract
The structural changes accompanying stretch-induced early unfolding events were investigated for the four type III fibronectin (FN-III) modules, FN-II I7, FN-IIIg, FN-III9, and FN-III10 by using steered molecular dynamics. Sim ulations revealed that two main energy barriers, I and II, have to be overc ome to initiate unraveling of FN-III's tertiary structure. In crossing the first barrier, the two opposing beta -sheets of FN-III are rotated against each other such that the beta -strands of both beta -sheets align parallel to the force Vector (aligned state). All further events in the unfolding pa thway proceed from this intermediate state. A second energy barrier has to be overcome to break the first major cluster of hydrogen bonds between adja cent beta -strands. Simulations revealed that the height of barrier I varie d significantly among the four modules studied, being largest for FN-III7 a nd lowest for FN-III10. whereas the height of barrier II showed little vari ation. Key residues affecting the mechanical stability of FN-III modules we re identified. These results suggest that FN-III modules can be prestretche d into an intermediate state with only minor changes to their tertiary stru ctures. FN-III10, for example, extends 12 Angstrom from the native "twisted " to the intermediate aligned state, and an additional 10 Angstrom from the aligned state to further unfolding where the first beta -strand is peeled away. The implications of the existence of intermediate states regarding th e elasticity of fibrillar