Miwa Naofumi, Kawamura Satoru
Department of Biology, Graduate School of Science, Osaka University, Osaka 560-0043, Japan.
Microsc Res Tech. 2003 Apr 15;60(6):593-9. doi: 10.1002/jemt.10301.
An S100-like calcium-binding protein, p26olf, was originally isolated from the frog (Rana Catesbeiana) olfactory epithelium with four chromatographical steps. The primary structure of p26olf contains two S100-like regions aligned in tandem with four functional EF-hands. At 100 mM K(+), wild-type p26olf binds Ca(2+) with a Kd value of 22 microM and a Hill coefficient of 2.0. Each EF-hand seems to have different affinity for Ca(2+): it is high in EF-A and -B and low in EF-C and -D. In our Ca(2+)-binding model, the order of Ca(2+)-binding to p26olf is EF-B, EF-A, EF-C, and EF-D. Expression of mRNA of p26olf is detected in various frog tissues: it is high in the olfactory epithelium, lung, and spleen, moderate in brain, retina, heart, and kidney, and low in liver and muscle. Immunohistochemical studies revealed that p26olf is prominently localized in the cilia of both olfactory and lung respiratory epithelium and especially enriched in the distal segment of the olfactory cilia. Several proteins in the olfactory cilia bind to p26olf in the presence of Ca(2+), suggesting that they are possible target proteins of p26olf. One of these target proteins is immunologically identified as a beta-adrenergic receptor kinase-like protein. In the olfactory cilia, p26olf may have some roles in the olfactory transduction or adaptation through interaction with this beta-adrenergic receptor kinase-like protein.
一种类似于S100的钙结合蛋白p26olf最初是通过四个色谱步骤从牛蛙（Rana Catesbeiana）的嗅觉上皮中分离出来的。p26olf的一级结构包含两个串联排列的S100样区域，带有四个功能性EF手基序。在100 mM K⁺条件下，野生型p26olf结合Ca²⁺的Kd值为22 μM，希尔系数为2.0。每个EF手基序对Ca²⁺的亲和力似乎不同：EF-A和-EF-B中的亲和力高，而EF-C和-EF-D中的亲和力低。在我们的Ca²⁺结合模型中，p26olf与Ca²⁺结合的顺序是EF-B、EF-A、EF-C和EF-D。在牛蛙的各种组织中均检测到p26olf的mRNA表达：在嗅觉上皮、肺和脾脏中表达较高，在脑、视网膜、心脏和肾脏中表达中等，在肝脏和肌肉中表达较低。免疫组织化学研究表明，p26olf主要定位于嗅觉和肺呼吸上皮的纤毛中，尤其在嗅觉纤毛的远端段富集。在Ca²⁺存在的情况下，嗅觉纤毛中的几种蛋白质与p26olf结合，表明它们可能是p26olf的靶蛋白。其中一种靶蛋白经免疫鉴定为β-肾上腺素能受体激酶样蛋白。在嗅觉纤毛中，p26olf可能通过与这种β-肾上腺素能受体激酶样蛋白相互作用，在嗅觉转导或适应过程中发挥一些作用。
