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標題: | 鮪魚與深海性黑龍魚視紫質基因之分子選殖與結構分析 Molecular cloning and structure analysis of the rhodopsin genes of tuna (Tunnus tonggol) and deep-sea black dragonfish (Idiacanthus antrostmus) |
作者: | Hann-chang Hsiung 熊漢昌 |
出版年 : | 2000 |
學位: | 碩士 |
摘要: | 視紫質蛋白(Rhodopsin, Rho)位於視網膜的視桿細胞,主要的功能是把外界環境的光線轉換成神經訊息,是脊椎動物感應弱光的主要分子。我們選擇了兩種生活在不同光譜環境的魚類作為實驗材料:第一種是棲息在水深 1000 至 5000 公尺深海的黑龍魚,該處只有微弱的藍光和生物螢光;第二種是大洋迴遊性的鮪魚,其生活在海水的表層。我們利用 extender PCR 的方法複殖了這兩種魚類的 Rho 基因,包括 5 端上游調控序列、 coding region 以及 3 端下游的序列。黑龍魚是第一種完整 Rho 基因被發表的深海魚類。 在Rho胺基酸序列的比對中發現,黑龍魚和鮪魚的 Rho 均保有在結構上或功能上重要、在各物種間均保守的胺基酸。在其影響吸收光譜的胺基酸方面,黑龍魚的 Rho 在第 83 和第 292 位置分別是 asparagine 及 serine,這兩個位置特殊的胺基酸可能造成 Rho 吸收光譜向短波長偏移,適應在深海微弱的藍光;而鮪魚 Rho 在第 83 和第 292 位置則為 aspartate 及 alanine,與其餘水錶層魚類的 Rho 相同。在Rho基因上游調控區域的序列比對中,發現黑龍魚和鮪魚的Rho基因均具有與哺乳動物、鳥類Rho基因 cis-element 相近的 BAT-1 核心序列(GGATTANZ2-5ATTA) (-120 to -90),以及在鯉魚 Rho 基因位於-52 to -46 處其 antisense 那一股的序列與哺乳動物Rho基因的 Ret-4 核心序列同源性極高的 GTAATCC (carp specific element)。然而在哺乳動物、鳥類和鯉魚 Rho 基因之間保守的 NRE element (-75 to -64),黑龍魚和鮪魚 Rho 基因卻只具有其前半段 TGCTGA 的同源;而不具有後半段 CAGCC 的同源。而因 CAGCC 是鯉魚視網膜核蛋白結合的位置,且不被哺乳動物 Nrl 抗體所辨認 (馬,1999),故推論魚類和哺乳動物結合在NRE上的核蛋白可能不盡相同,且作用在不同的位置上。 The main function of rhodopsin (Rho) that located in rod cells of retina is to transfer the light of outer environment into nervous signal. Rho is the main molecule to detect the dim light. Two kinds of fish lived in different spectral environments are chosen as the experimental materials. The first one is black dragonfish habitated in the deep sea at depth 1000 to 5000 m, where only weak blue light and bioluminescence exist. The second is tuna lived in the surface of ocean. The extender PCR is employed to clone the Rho genes of the two kinds of fish which included 5’ upstream regulatory region, coding region and 3’ downstream sequences. The black dragonfish is the first deep-sea fish whose Rho gene has been published. From the comparison of the deduced amino acid sequence, it revealed that both tuna and black dragonfish maintain some amino acids of structural or functional importance are conserved among species. The positions 83 and 292 of black dragonfish Rho are asparagine and serine, and the two special amino acids may cause Rho absorption spectrum to shift to short wavelength and adapt to deep-sea weak blue light. For the tuna, the positions 83 and 292 of Rho are aspartate and alanine, are the same as other surface-dwelling fish. From the comparison of Rho gene upstream regulatory region, it revealed that both the Rho genes of tuna and dragonfish have the BAT-1 core sequence (GGATTN2-5ATTA) (-120 to -90) similar to that of mammals and birds. We also found homologous sequences of carp specific element GTAATCC (-52 to -46) which antisense sequences are homologous to the core sequences of Ret-4 in mammals. There are conservative NRE element (-75 to -64) existing between the Rho gene of mammals, birds and carp. However, black dragonfish and tuna have only the former half homologous segment TGCTGA, not the later half segment. Because CAGCC is the binding site of carp nuclear proteins and is not recognized by the Nrl antibodies of mammals (Ma, 1999), hence, it is presumed that nuclear proteins binding on the NRE of fishes and mammals are probably not the same and act on different locations. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/75155 |
全文授權: | 未授權 |
顯示於系所單位: | 漁業科學研究所 |
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