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Stabilization provided by neighboring strands is critical for the mechanical stability of proteins

TitleStabilization provided by neighboring strands is critical for the mechanical stability of proteins
Publication TypeJournal Article
Year of Publication2008
AuthorsSharma, D, Feng, G, Khor, D, Genchev, GZ, Lu, H, Li, HB
JournalBiophysical Journal
Volume95
Pagination3935-3942
Date PublishedOct
Type of ArticleArticle
ISBN Number0006-3495
KeywordsBARSTAR, DYNAMICS SIMULATIONS, IMMUNOGLOBULIN DOMAINS, MICROSCOPE, MOLECULE FORCE SPECTROSCOPY, resistance, SINGLE PROTEIN, TITIN, TOPOLOGY, UBIQUITIN
Abstract

Single-molecule force spectroscopy studies and steered molecular dynamics simulations have revealed that protein topology and pulling geometry play important roles in determining the mechanical stability of proteins. Most studies have focused on local interactions that are associated with the force-bearing beta-strands. Interactions mediated by neighboring strands are often overlooked. Here we use Top7 and barstar as model systems to illustrate the critical importance of the stabilization effect provided by neighboring beta-strands on the mechanical stability. Using single-molecule atomic force microscopy, we showed that Top7 and barstar, which have similar topology in their force-bearing region, exhibit vastly different mechanical-stability characteristics. Top7 is mechanically stable and unfolds at similar to 150 pN, whereas barstar is mechanically labile and unfolds largely below 50 pN. Steered molecular dynamics simulations revealed that stretching force peels one force-bearing strand away from barstar to trigger unfolding, whereas Top7 unfolds via a substructure-sliding mechanism. This previously overlooked stabilization effect from neighboring beta-strands is likely to be a general mechanism in protein mechanics and can serve as a guideline for the de novo design of proteins with significant mechanical stability and novel protein topology.

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