Kachar B, Parakkal M, Kurc M, Zhao Y, Gillespie P G
Section on Structural Cell Biology, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892-4163, USA.
Proc Natl Acad Sci U S A. 2000 Nov 21;97(24):13336-41. doi: 10.1073/pnas.97.24.13336.
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.
毛细胞对转导通道的门控显然需要一个门控弹簧，这是一种将力传递给通道的弹性元件。为了确定门控弹簧是否是顶连，即沿着机械敏感轴连接两个静纤毛的细丝，我们通过快速冷冻、深蚀刻电子显微镜在高分辨率下检查了顶连的结构。我们发现顶连是一条右手螺旋的双股细丝，在接触较高静纤毛之前通常会分叉成两个分支；在另一端，几根短细丝从较短的静纤毛延伸到顶连。顶连的结构表明它要么是一种螺旋聚合物，要么是一对编织的丝状大分子，因此可能相对坚硬且不可伸长。这种行为与测得的门控弹簧的弹性不相符，这表明门控弹簧反而与顶连的螺旋段串联。
