Coutinho P, Goodyear R, Legan P K, Richardson G P
School of Biological Sciences, University of Sussex, Falmer, Brighton, UK.
Hear Res. 1999 Apr;130(1-2):62-74. doi: 10.1016/s0378-5955(98)00213-5.
The avian and mammalian tectorial membranes both contain two non-collagenous glycoproteins, alpha and beta-tectorin. To determine whether variations in the primary sequences of the chick and mouse alpha-tectorins account for differences in subunit composition and matrix structure of the tectorial membranes in these two species, cDNAs spanning the entire open reading frame of chick alpha-tectorin were cloned and the derived amino acid sequence was compared with that of mouse alpha-tectorin. Chick alpha-tectorin shares 73% amino acid sequence identity with mouse alpha-tectorin and, like mouse alpha-tectorin, is composed of three distinct modules: an N-terminal region similar to the G1 domain of entactin, a central region that shares identity with zonadhesin and contains three full and two partial von Willebrand factor type D repeats, and a C-terminal region containing a zona pellucida domain. The central region of chick alpha-tectorin contains fewer potential N-glycosylation sites than that of mouse alpha-tectorin and is cleaved at two additional sites. Differences in the glycosylation and proteolytic processing of chick and mouse alpha-tectorin may therefore account for the variation observed in the composition and structure of the collagenase-insensitive matrices of the avian and mammalian tectorial membranes. In situ hybridisation and Northern blot analysis of chick inner ear tissue indicate that the spatial and temporal patterns of alpha and beta-tectorin mRNA expression in the developing chick inner ear are different, suggesting the two tectorins may each form homomeric filaments.
鸟类和哺乳动物的盖膜均含有两种非胶原蛋白糖蛋白，即α-和β-耳纤毛蛋白。为了确定鸡和小鼠α-耳纤毛蛋白一级序列的差异是否导致这两个物种盖膜亚基组成和基质结构的不同，克隆了跨越鸡α-耳纤毛蛋白整个开放阅读框的cDNA，并将推导的氨基酸序列与小鼠α-耳纤毛蛋白的序列进行比较。鸡α-耳纤毛蛋白与小鼠α-耳纤毛蛋白的氨基酸序列一致性为73%，并且与小鼠α-耳纤毛蛋白一样，由三个不同的模块组成：一个类似于巢蛋白G1结构域的N端区域、一个与带状粘连蛋白具有同源性且包含三个完整和两个部分的血管性血友病因子D型重复序列的中央区域，以及一个包含透明带结构域的C端区域。鸡α-耳纤毛蛋白的中央区域比小鼠α-耳纤毛蛋白含有更少的潜在N-糖基化位点，并且在另外两个位点被切割。因此，鸡和小鼠α-耳纤毛蛋白在糖基化和蛋白水解加工方面的差异可能解释了在鸟类和哺乳动物盖膜的胶原酶不敏感基质的组成和结构中观察到的变化。鸡内耳组织的原位杂交和Northern印迹分析表明，发育中的鸡内耳中α-和β-耳纤毛蛋白mRNA表达的空间和时间模式不同，这表明这两种耳纤毛蛋白可能各自形成同聚体细丝。
