Ligand binding and inhibition of an oxygen-sensitive soluble guanylate cyclase, Gyc-88E, from Drosophila
Ligand binding and inhibition of an oxygen-sensitive soluble guanylate cyclase, Gyc-88E, from Drosophila
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DOI：
10.1021/bi701771r
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发表时间：
2007-12-25
期刊：
影响因子：
2.9
通讯作者：
Marletta, Michael A.
中科院分区：
文献类型：
--
作者：
Huang, Shirley H.;Rio, Donald C.;Marletta, Michael A.
可溶性鸟苷酸环化酶（sGC）使用亚铁血红素辅助因子作为NO的受体，一旦结合激活酶将GTP转化为cGMP。sGC中的血红素辅助因子不结合氧，因此尽管细胞氧浓度（mu M）远高于一氧化氮的信号浓度（nM），但它仍能选择性地结合NO。这种对氧的配体歧视的分子细节已经出现，并允许对sGC家族的配体特异性进行预测。本文报道的结果表明，来自果蝇的Gyc-88E是一种结合氧、NO和CO的血红蛋白。这三种配体形成6位配合物。Gyc-88E作为同型二聚体具有活性(5600 +/- 243 nmol min(-1) mg(-1))，被O-2、CO和NO抑制（分别为3.2倍、2.9倍和2倍）。空气条件下（273 μ M氧气）GTP的K-m为0.66 +/- 0.15 mM，厌氧条件下为0.82 +/- 0.15 mM。氧的K-i计算为51 +/- 28 μ m。Gyc-88E的生化特性是鸟苷酸环化酶所特有的，表明它可能具有氧传感器的功能。
Soluble guanylate cyclase (sGC) uses a ferrous heme cofactor as a receptor for NO and once bound activates the enzyme for the conversion of GTP to cGMP. The heme cofactor in sGC does not bind oxygen, thereby allowing it to selectively bind NO despite a cellular concentration of oxygen (mu M) that is much higher than signaling concentrations of nitric oxide (nM). The molecular details of this ligand discrimination against oxygen have emerged and allowed for predictions regarding ligand specificity in the sGC family. The results reported here show that Gyc-88E from Drosophila is a hemoprotein that binds oxygen, as well as NO and CO. All three ligands form 6-coordinate complexes. Gyc-88E is active as a homodimer (5600 +/- 243 nmol min(-1) mg(-1)) and is inhibited by O-2, CO, and NO (3.2-, 2.9-, and 2-fold, respectively). The K-m for GTP was 0.66 +/- 0.15 mM in air (273 mu M oxygen) and 0.82 +/- 0.15 mM under anaerobic conditions. The K-i for oxygen was calculated to be 51 +/- 28 mu M. The biochemical properties of Gyc-88E are unique for guanylate cyclases and suggest a possible function as an oxygen sensor.