A Study on the Molecular Evolution and Functional Adaptation of

• Main Authors: Juang, Bi-Tzen, 莊碧簪
• Other Authors: Daniel T.-b. Shih
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/79379652598275731504

碩士 === 台北醫學院 === 細胞及分子生物研究所 === 84 === 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.