title: Probing the folded state of fibronectin type III domains in stretched fibrils by measuring buried cysteine accessibility.
abstract: Fibronectin (FN) is an extracellular matrix protein that is assembled into fibrils by cells during tissue morphogenesis and wound healing. FN matrix fibrils are highly elastic, but the mechanism of elasticity has been debated: it may be achieved by mechanical unfolding of FN-III domains or by a conformational change of the molecule without domain unfolding. Here, we investigate the folded state of FN-III domains in FN fibrils by measuring the accessibility of buried cysteines. Four of the 15 FN-III domains (III-2, -3, -9, and -11) appear to unfold in both stretched fibrils and in solution, suggesting that these domains spontaneously open and close even in the absence of tension. Two FN-III domains (III-6 and -12) appear to unfold only in fibrils and not in solution. These results suggest that domain unfolding can at best contribute partially to the 4-fold extensibility of fibronectin fibrils.
authors.affiliation: Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710, USA. christopher.lemmon@duke.edu
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Lemmon
authors.forename: Tomoo
authors.initials: T
authors.lastname: Ohashi
authors.forename: Harold P
authors.initials: HP
authors.lastname: Erickson
mesh_terms: D000818:Animals; D003545:Cysteine / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004548:Elasticity; D005353:Fibronectins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D017510:Protein Folding; D017434:Protein Structure, Tertiary
chemical_list: D005353:Fibronectins; D003545:Cysteine