鱧魚 (Channa maculata) 血紅蛋白之分子演 化及功能適應性研究

鱧魚 (Channa maculata) 血紅蛋白之分子演 化及功能適應性研究

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，用離子交換樹脂層析法分離全血溶物（ whole trait ），得一主要血

紅蛋白組成（ Hb I ）及三種微量的血紅蛋白組成（ HbIx ， Hb II 及 Hb III ）。 膠質層析法的數據指出 Hb I 具有四聚體低解離的特性。分析 其氧合平衡性質得知鱧魚血紅蛋白已具有部份陸上動物血紅蛋白的特性，

其氧氣輸送機能受細胞內 ATP 之調控，其氫離子之影響能隨溫而變，有 益於鱧魚之兩棲呼吸。這些功能特性之結構基礎可由其部份氨基酸序列來 解釋。 為了知曉鱧魚血紅蛋白之球蛋白（ globin ）的氨基酸序列，

所以我們從求得其 cDNA 序列著手。 由鱧魚全血中抽取細胞總和 RNA ，經 反轉錄反應及聚合 鏈鎖反應已經可得

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中之分析的結果提供了鱧魚血紅蛋白適應兩棲呼吸在分子層面上如何演變 及修飾之說明。

A Study on the Molecular Evolution and Functional Adaptation of

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Snakehead fish (Channa maculata) is a bimodal breathing fish, able to acquire oxygen from water as well from air directly.

Hemoglobin of this fish may therefore be an excellent model for illustrating the functional aspect of the structural evolution in respiratory protein. To date, however, neither the structure nor the oxygen transport properties of this respiratory hemoglobin has been L 嬙 rted yet. To gain insights into the allosteric nature of this fish hemoglobin, we have conducted a series of structure and oxygen equilibrium studies. We have isolated a major hemoglobin (HbI) and three minor hemoglobins (HbIx, HbII, and HbIII)from the whole trait using an ion-

exchange chromatography. A gel chromatography was employed to characterize the stability and dissociation rate of HbI

tetramer. An automatic recording oxygen equilibrium analyzer was used to characterize the oxygen transport function of

hemoglobins. Hemoglobin of snakehead fish exhibits functional

characteristics in between the air breathing and the water

breathing respiratory protein. Its oxygen transport is primarily

regulated by the cellular phosphates, especially ATP. Exhibiting

no Root effect and a reduced alkaline Bohr effect. A partial

protein sequence corresponding the phosphate binding has been

determined to confirm the structural basis this functional

characterize. On the other hand, the influence of proton on the

oxygen transport function in this fish hemoglobin is temperature

dependent. Results obtained from this study provide a better

insight into the benefit for the snakehead fish in adapting

bimodal breathing. Explaination of the structural basis of ATP

as a strong effect is aided by a partial amino acid sequence

determination analysis. The data provide an elueidation of how

the snakehead fish hemoglobin is designed to adapt the air

breathing at the molecular level.