Hagner-Holler Silke, Schoen Axel, Erker Wolfgang, Marden James H, Rupprecht Rainer, Decker Heinz, Burmester Thorsten
Institutes of Zoology and Molecular Biophysics, Johannes Gutenberg University of Mainz, 55099 Mainz, Germany.
Proc Natl Acad Sci U S A. 2004 Jan 20;101(3):871-4. doi: 10.1073/pnas.0305872101. Epub 2004 Jan 8.
Insects possess an elaborate tracheal system that enables transport of gaseous oxygen from the atmosphere directly to the inner organs. Therefore, the presence of specialized oxygen-transport proteins in the circulatory system of insects has been considered generally unnecessary. Here, we show for the first time, to our knowledge, the presence of an ancestral and functional hemocyanin (Hc) in an insect. In the hemolymph of nymphs and adults of the stonefly Perla marginata, a hexameric Hc was identified, which consists of two distinct subunit types of 659 and 655 amino acids. P. marginata Hc displays cooperative oxygen binding with a moderately high oxygen affinity [(half-saturation pressure, P(50) approximately 8 torr (1 torr = 133 Pa)]. No evidence was found for the presence of Hcs in the more evolutionarily advanced holometabolan insects, suggesting that this type of respiratory protein was lost later in insect evolution. However, our results demonstrate that, in contrast to the accepted paradigm, certain basal insects have retained an ancestral blood-based mechanism of gas exchange.
昆虫拥有一套复杂的气管系统，该系统能够将气态氧从大气中直接输送到内部器官。因此，昆虫循环系统中存在专门的氧运输蛋白通常被认为是不必要的。在此，据我们所知，我们首次证明了一种昆虫中存在一种原始且具有功能的血蓝蛋白（Hc）。在石蝇Perla marginata若虫和成虫的血淋巴中，鉴定出一种六聚体Hc，它由两种不同的亚基类型组成，分别含有659和655个氨基酸。P. marginata Hc表现出协同氧结合，具有中等偏高的氧亲和力[（半饱和压力，P(50)约为8托（1托 = 133帕）]。在进化程度更高的全变态昆虫中未发现血蓝蛋白存在的证据，这表明这种呼吸蛋白在昆虫进化后期丢失了。然而，我们的结果表明，与公认的模式相反，某些基础昆虫保留了一种基于血液的原始气体交换机制。
