Matsuura M S, Ogo S H, Focesi A
Comp Biochem Physiol A Comp Physiol. 1987;86(4):683-7. doi: 10.1016/0300-9629(87)90624-4.
Hemoglobin from the water-snake Liophis miliaris in the stripped form presents high oxygen affinity of about P50 = 1 mmHg and Hill coefficient of about 1.0 at pH from 6.8 to 8.5. In the presence of ATP such values become P50 = 20 mmHg and nH about 2.0, respectively, at low pH from 6.5 to 7.5. When the pH increases an abrupt decrease of both P50 and nH values occurs falling close to those found for the stripped hemoglobin. Gel-filtration in Sephadex G-100 equilibrated with 0.05 M Tris-HCl buffer containing 1 mM EDTA of the stripped hemoglobin show the presence of only one component of mol. wt of about 32,500 dt similar to the dimer of human hemoglobin A. The deoxy form of the dimer previously treated with ATP and placed on Sephadex column in the same condition but containing 1 mM IHP emerges as tetramer with mol. wt similar to that found for human hemoglobin, i.e. of about 65,000 dt. Results of the multiplicity of the snake hemoglobin, as well as the large alkaline Bohr effect in the presence of ATP previously reported, seems to be inconsistent due to the dimer-tetramer transition that occurs when ATP is bound to the stripped hemoglobin. A molecular mechanism involving the dimer-tetramer transition is proposed to described the oxygen transport in these animals.
水蛇Liophis miliaris的去辅基血红蛋白在pH值为6.8至8.5时呈现出高氧亲和力，P50约为1 mmHg，希尔系数约为1.0。在ATP存在的情况下，在pH值为6.5至7.5时，这些值分别变为P50 = 20 mmHg和nH约为2.0。当pH值升高时，P50和nH值会突然下降，接近去辅基血红蛋白的值。用含有1 mM EDTA的0.05 M Tris-HCl缓冲液平衡的Sephadex G-100对去辅基血红蛋白进行凝胶过滤，结果显示仅存在一种分子量约为32,500道尔顿的成分，类似于人血红蛋白A的二聚体。先前用ATP处理并置于相同条件但含有1 mM IHP的Sephadex柱上的二聚体的脱氧形式以分子量与人血红蛋白相似（即约65,000道尔顿）的四聚体形式出现。先前报道的蛇血红蛋白的多重性结果以及在ATP存在下的大碱性玻尔效应，由于ATP与去辅基血红蛋白结合时发生的二聚体 - 四聚体转变，似乎并不一致。提出了一种涉及二聚体 - 四聚体转变的分子机制来描述这些动物中的氧运输。
