Prestin forms oligomer with four mechanically independent subunits.
Prestin forms oligomer with four mechanically independent subunits.
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DOI：
10.1016/j.brainres.2010.03.070
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发表时间：
2010-05-28
期刊：
影响因子：
2.9
通讯作者：
He, David Z. Z.
中科院分区：
文献类型：
--
作者：
Wang, Xiang;Yang, Shiming;Jia, Shuping;He, David Z. Z.
Prestin是耳蜗外毛细胞的运动蛋白，具有直接、快速和相互作用的机电转换功能。Prestin由744个氨基酸组成，相对分子质量为81.4 kDa。预测的单个prestin分子的膜拓扑结构和分子质量似乎不足以解释OHC膜中表达的膜内颗粒(IMP)的大小。尽管最近的生化证据表明Prestin形成同源低聚物，很可能是以四聚体的形式存在，但Prestin在毛细胞中的寡聚结构仍然不清楚。通过测量它们的非线性电容(NLC)，我们得到了沙土鼠毛囊中Prestin的电荷密度。测得的平均电荷密度(22,608μm−2)是冷冻断裂研究中报道的平均电荷密度(5,686μm−2)的四倍。这表明，每个IMP包含四个prestin分子，基于每个prestin转移单一基元电荷的一般概念。随后，我们比较了NLC的电压依赖性和同时测量的NLC和体细胞运动的斜率因子值，以确定NLC和运动是否完全耦合以及prestin亚单位在四聚体中如何发挥作用。我们发现NLC和运动性的电压依赖性和斜率因子没有统计学上的差异，表明NLC和运动性是完全耦合的。NLC和运动之间的斜率因子相同的事实表明，四聚体中的每个Prestin单体是平行的，每个单体都独立地与细胞质或其他伙伴相互作用，以促进机械反应。
Prestin is the motor protein of cochlear outer hair cells (OHCs) with the unique capability of performing direct, rapid and reciprocal electromechanical conversion. Prestin consists of 744 amino acids with a molecular mass of ~81.4 kDa. The predicted membrane topology and molecular mass of a single prestin molecule appear inadequate to account for the size of intramembrane particles (IMPs) expressed in the OHC membrane. Although recent biochemical evidence suggests that prestin forms homo-oligomers, most likely as a tetramer, the oligomeric structure of prestin in OHCs remains unclear. We obtained the charge density of prestin in the gerbil OHCs by measuring their nonlinear capacitance (NLC). The average charge density (22,608 μm−2) measured was four times the average IMP density (5,686 μm−2) reported in the freeze-fracture study. This suggests that each IMP contains four prestin molecules, based on the general notion that each prestin transfers a single elementary charge. We subsequently compared the voltage dependency and the values of slope factor of NLC and somatic motility simultaneously measured from the same OHCs to determine whether NLC and motility are fully coupled and how prestin subunits function within the tetramer. We showed that the voltage dependency and slope factors of NLC and motility were not statistically different, suggesting that NLC and motility are fully coupled. The fact that the slope factor is the same between NLC and motility suggests that each prestin monomer in the tetramer is in parallel, each interacting independently with cytoplasmic or other partners to facilitate the mechanical response.
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