title: Stepwise unfolding of ankyrin repeats in a single protein revealed by atomic force microscopy.
abstract: Using single-molecule atomic force microscopy, we find that a protein consisting of six identical ankyrin repeat units flanked by N- and C-terminal modules (N6C) unfolds in a stepwise, unit-by-unit fashion under a mechanical force. Stretching a N6C molecule results in a sawtooth pattern fingerprint, with as many as six peaks separated by approximately 10 nm and an average unfolding force of 50 +/- 20 pN. Our results demonstrate that a stretching force can unfold multiple repeat units individually in a single protein molecule, despite extensive hydrophobic interactions between adjacent units.
authors.forename: Lewyn
authors.initials: L
authors.lastname: Li
authors.forename: Svava
authors.initials: S
authors.lastname: Wetzel
authors.forename: Andreas
authors.initials: A
authors.lastname: Plückthun
authors.forename: Julio M
authors.initials: JM
authors.lastname: Fernandez
mesh_terms: D017089:Ankyrin Repeat; D018625:Microscopy, Atomic Force; D017510:Protein Folding; D011506:Proteins / Q000737:chemistry* / Q000648:ultrastructure
chemical_list: D011506:Proteins