Identification of a tyrosine switch in copper-haem nitrite reductases.
Identification of a tyrosine switch in copper-haem nitrite reductases.
复制标题
DOI：
10.1107/s2052252518008242
复制
发表时间：
2018-07-01
期刊：
影响因子：
3.9
通讯作者：
Hasnain SS
中科院分区：
文献类型：
--
作者：
Dong J;Sasaki D;Eady RR;Antonyuk SV;Hasnain SS
Pickettii(RpNiR)的亚硝酸铜还原酶(Haem CuNiR)的结构特征表明，酪氨酸残基阻断了底物进入通道和结合部位。对含NO晶体的处理触发了酪氨酸的运动，使NO和NO2−结合的物种能够被捕获，从而提供了关于这类亚硝酸盐还原酶中配体结合物种的第一个信息。使用酪氨酸作为激活氧化还原酶RpNiR的开关可能具有更广泛的意义，因为这种酪氨酸在所有已知的血红蛋白CuNiR中都是完全保守的。很少有案例表明酪氨酸参与催化或控制催化，尽管它有能力在更高的电位下进行化学(1 V对NHE)。结果表明，硝酸拉氏菌(RpNiR)晶体与一氧化氮(NO)(−0.8±0.2 V)作用后，阻断铜血红素亚硝酸还原酶中疏水底物进入通道的酪氨酸可以像开关一样被激活。在没有任何结果的情况下，由于Tyr323从AspCAT97旋转而产生的通道打开。值得注意的是，尽管没有2型铜(T2Cu)，但催化缺铜酶的结构也显示Tyr323处于闭合位置，这清楚地表明Tyr323的状态不受T2Cu或其氧化还原化学的控制。研究还表明，NO的激活不是通过与血红素结合来实现的。有人认为，Tyr323开关的激活是由NO通过从酪氨酸中提取质子和形成HNO来控制的。在这里获得的关于使用酪氨酸作为催化的开关的见解对生物学中的催化具有更广泛的意义。
Structural characterization of the copper-haem nitrite reductase (haem CuNiR) from Ralstonia pickettii (RpNiR) revealed a tyrosine residue blocking the substrate-entry channel and binding site. The treatment of crystals with NO triggers a movement of tyrosine that allows NO- and NO2 −-bound species to be captured to provide the first information on ligand-bound species in this class of nitrite reductases. The use of tyrosine as a switch in activating the redox enzyme RpNiR may have wider significance as this tyrosine is found to be totally conserved in all known haem CuNiRs. There are few cases where tyrosine has been shown to be involved in catalysis or the control of catalysis despite its ability to carry out chemistry at much higher potentials (1 V versus NHE). Here, it is shown that a tyrosine that blocks the hydrophobic substrate-entry channel in copper-haem nitrite reductases can be activated like a switch by the treatment of crystals of Ralstonia pickettii nitrite reductase (RpNiR) with nitric oxide (NO) (−0.8 ± 0.2 V). Treatment with NO results in an opening of the channel originating from the rotation of Tyr323 away from AspCAT97. Remarkably, the structure of a catalytic copper-deficient enzyme also shows Tyr323 in the closed position despite the absence of type 2 copper (T2Cu), clearly demonstrating that the status of Tyr323 is not controlled by T2Cu or its redox chemistry. It is also shown that the activation by NO is not through binding to haem. It is proposed that activation of the Tyr323 switch is controlled by NO through proton abstraction from tyrosine and the formation of HNO. The insight gained here for the use of tyrosine as a switch in catalysis has wider implications for catalysis in biology.