Zeis Bettina, Becher Bertram, Goldmann Torsten, Clark Ryan, Vollmer Ekkehard, Bölke Birgit, Bredebusch Ilona, Lamkemeyer Tobias, Pinkhaus Olaf, Pirow Ralph, Paul Rüdiger J
Institut für Zoophysiologie, Westfälische Wilhelms-Universität Münster, D-48143 Münster, Germany.
Biol Chem. 2003 Aug;384(8):1133-45. doi: 10.1515/BC.2003.126.
The quantity and quality of the haemoglobin (Hb) of Daphnia magna is related to oxygen partial pressure in the water. Both the dynamics of hypoxia-induced Hb gene transcription, as well as Hb properties in animals incubated long-term at hyperoxia, normoxia and hypoxia, were investigated. Examination of Hb gene (dhb1-dhb3) transcription showed the expression of dhb2 and especially dhb3 to increase markedly approximately one hour after the onset of hypoxia, whereas dhb1 was expressed more or less constitutively. At an incubation close to anoxia, an onset of dhb3 transcription was found already after two minutes. In long-term incubated animals, concentration and oxygen affinity of Hb were lower at higher oxygen partial pressures. With decreasing oxygen availability, the subunit composition of Hb macromolecules changed. The share of the dhb2-encoded subunit, DHbF, increased already during moderate hypoxia. The increase of dhb3 mRNA (encoding DHbC) may be related to a transient increase of DHbC in the first days of hypoxia and/or to an additional coding of dhb3 for DHbD. The rise of DHbD, and particularly DHbA, only at severe hypoxia coincided with the increase of Hb oxygen affinity. The dhb1-encoded subunits DHbB and DHbE showed either a relatively moderate increase or even a decrease in concentration at hypoxia. In small animals with restricted homeostasis capabilities such as Daphnia, adaptation of the protein equipment seems to be a more effective strategy than allosteric modulator control.
大型溞血红蛋白（Hb）的数量和质量与水中的氧分压有关。研究了低氧诱导的Hb基因转录动态，以及在高氧、常氧和低氧条件下长期培养的动物体内Hb的特性。对Hb基因（dhb1 - dhb3）转录的检测表明，低氧开始后约一小时，dhb2尤其是dhb3的表达显著增加，而dhb1的表达或多或少是组成型的。在接近缺氧的培养条件下，两分钟后就发现了dhb3转录的开始。在长期培养的动物中，较高氧分压下Hb的浓度和氧亲和力较低。随着氧供应的减少，Hb大分子的亚基组成发生变化。在中度低氧期间，由dhb2编码的亚基DHbF的比例就已经增加。dhb3 mRNA（编码DHbC）的增加可能与低氧最初几天DHbC的短暂增加和/或dhb3额外编码DHbD有关。仅在严重低氧时DHbD尤其是DHbA的增加与Hb氧亲和力的增加相吻合。在低氧条件下，由dhb1编码的亚基DHbB和DHbE的浓度要么相对适度增加，要么甚至降低。在像大型溞这样体内稳态能力有限的小动物中，蛋白质装备的适应性似乎是比变构调节剂控制更有效的策略。
