Oxygen Supply from the Bird's Eye Perspective GLOBIN E IS A RESPIRATORY PROTEIN IN THE CHICKEN RETINA
Oxygen Supply from the Bird's Eye Perspective GLOBIN E IS A RESPIRATORY PROTEIN IN THE CHICKEN RETINA
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DOI：
10.1074/jbc.m111.224634
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发表时间：
2011-07-29
影响因子：
4.8
通讯作者：
Burmester, Thorsten
中科院分区：
文献类型：
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作者：
Blank, Miriam;Kiger, Laurent;Burmester, Thorsten
脊椎动物眼睛的视觉过程需要大量的代谢能量，因此需要氧气。鸟类视网膜的氧气供应是一项具有挑战性的任务，因为鸟类眼睛大，视网膜厚，代谢率高，但既没有深层视网膜也没有浅层毛细血管。呼吸道蛋白质如肌红蛋白可以增强对某些组织的氧气供应，因此哺乳动物的视网膜含有大量的神经红蛋白。珠蛋白E（Globin E，GbE）是近年来发现的鸡眼特异性珠蛋白。在斑胸草雀和火鸡基因组中发现了Orthopathy GbE基因，但在非鸟类脊椎动物中似乎不存在。珠蛋白同源性和基因同线性的分析表明，GbE的古老起源，但没有帮助分配到任何特定的珠蛋白类型。我们发现，鸡视网膜的感光细胞具有高水平的GbE蛋白，其在整个眼睛中积累到接近10 μ M。实时定量RT-PCR显示，眼睛中的GbE mRNA水平比大脑中高出50，000倍。重组鸡GbE的光谱分析和配体结合动力学揭示了具有P-50 = 5.8torrs（25 ℃）和15 torrs（41 ℃）的氧亲和力的五配位球蛋白。这些数据共同表明，GbE有助于维持鸟类视网膜的氧气供应。
The visual process in the vertebrate eye requires high amounts of metabolic energy and thus oxygen. Oxygen supply of the avian retina is a challenging task because birds have large eyes, thick retinae, and high metabolic rates but neither deep retinal nor superficial capillaries. Respiratory proteins such as myoglobin may enhance oxygen supply to certain tissues, and thus the mammalian retina harbors high amounts of neuroglobin. Globin E (GbE) was recently identified as an eye-specific globin of chicken (Gallus gallus). Orthologous GbE genes were found in zebra finch and turkey genomes but appear to be absent in non-avian vertebrate classes. Analyses of globin phylogeny and gene synteny showed an ancient origin of GbE but did not help to assign it to any specific globin type. We show that the photoreceptor cells of the chicken retina have a high level ofGbE protein, which accumulates to similar to 10 mu M in the total eye. Quantitative real-time RT-PCR revealed an similar to 50,000-fold higher level of GbE mRNA in the eye than in the brain. Spectroscopic analysis and ligand binding kinetics of recombinant chicken GbE reveal a penta-coordinated globin with an oxygen affinity of P-50 = 5.8 torrs at 25 degrees C and 15 torrs at 41 degrees C. Together these data suggest that GbE helps to sustain oxygen supply to the avian retina.