title: A mechanical unfolding intermediate in an actin-crosslinking protein.
abstract: Many F-actin crosslinking proteins consist of two actin-binding domains separated by a rod domain that can vary considerably in length and structure. In this study, we used single-molecule force spectroscopy to investigate the mechanics of the immunoglobulin (Ig) rod domains of filamin from Dictyostelium discoideum (ddFLN). We find that one of the six Ig domains unfolds at lower forces than do those of all other domains and exhibits a stable unfolding intermediate on its mechanical unfolding pathway. Amino acid inserts into various loops of this domain lead to contour length changes in the single-molecule unfolding pattern. These changes allowed us to map the stable core of approximately 60 amino acids that constitutes the unfolding intermediate. Fast refolding in combination with low unfolding forces suggest a potential in vivo role for this domain as a mechanically extensible element within the ddFLN rod.
authors.affiliation: Lehrstuhl für Angewandte Physik, Ludwig-Maximilians-Universität München, Amalienstrasse 54, 80799 München, Germany.
authors.forename: Ingo
authors.initials: I
authors.lastname: Schwaiger
authors.forename: Angelika
authors.initials: A
authors.lastname: Kardinal
authors.forename: Michael
authors.initials: M
authors.lastname: Schleicher
authors.forename: Angelika A
authors.initials: AA
authors.lastname: Noegel
authors.forename: Matthias
authors.initials: M
authors.lastname: Rief
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D003285:Contractile Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D003432:Cross-Linking Reagents; D004023:Dictyostelium / Q000235:genetics / Q000378:metabolism; D019281:Dimerization; D064448:Filamins; D066298:In Vitro Techniques; D008840:Microfilament Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018625:Microscopy, Atomic Force; D016297:Mutagenesis, Site-Directed; D011489:Protein Denaturation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D000199:Actins; D003285:Contractile Proteins; D003432:Cross-Linking Reagents; D064448:Filamins; D008840:Microfilament Proteins; D015800:Protozoan Proteins