title: High-resolution structure of hair-cell tip links.
abstract: Transduction-channel gating by hair cells apparently requires a gating spring, an elastic element that transmits force to the channels. To determine whether the gating spring is the tip link, a filament interconnecting two stereocilia along the axis of mechanical sensitivity, we examined the tip link's structure at high resolution by using rapid-freeze, deep-etch electron microscopy. We found that the tip link is a right-handed, coiled double filament that usually forks into two branches before contacting a taller stereocilium; at the other end, several short filaments extend to the tip link from the shorter stereocilium. The structure of the tip link suggests that it is either a helical polymer or a braided pair of filamentous macromolecules and is thus likely to be relatively stiff and inextensible. Such behavior is incompatible with the measured elasticity of the gating spring, suggesting that the gating spring instead lies in series with the helical segment of the tip link.
authors.affiliation: Section on Structural Cell Biology, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892-4163, USA. kachab@nidcd.nih.gov
authors.forename: B
authors.initials: B
authors.lastname: Kachar
authors.forename: M
authors.initials: M
authors.lastname: Parakkal
authors.forename: M
authors.initials: M
authors.lastname: Kurc
authors.forename: Y
authors.initials: Y
authors.lastname: Zhao
authors.forename: P G
authors.initials: PG
authors.lastname: Gillespie
mesh_terms: D000818:Animals; D002645:Chickens; D003051:Cochlea / Q000648:ultrastructure; D005613:Freeze Etching; D005614:Freeze Fracturing; D006168:Guinea Pigs; D006198:Hair Cells, Auditory / Q000502:physiology / Q000648:ultrastructure*; D008854:Microscopy, Electron; D011892:Rana catesbeiana; D012444:Saccule and Utricle / Q000648:ultrastructure; D014722:Vestibule, Labyrinth / Q000648:ultrastructure