Marinobacter hydrocarbonoclasticus nitric oxide reductase, cNOR, is an integral membrane protein composed of two subunits with different roles, NorC (electron transfer) and NorB (catalytic) that receives electrons from the soluble cytochrome c₅₅₂ and reduces nitric oxide to nitrous oxide in the denitrification pathway. The solvent-exposed domain of NorC, harboring a c-type heme was heterologously produced, along with its physiological electron donor, cytochrome c₅₅₂. These two proteins were spectroscopically characterized and shown to be similar to the native proteins, both being low-spin and Met-His coordinated, with the soluble domain of NorC presenting some additional features of a high-spin heme, which is consistent with the higher solvent accessibility of its heme and weaker coordination of the methionine axial ligand. The electron transfer complex between the two proteins has a 1:1 stoichiometry, and an upper limit for the dissociation constant was estimated by ¹H NMR titration to be 1.2 ± 0.4 μM. Electrochemical techniques were used to characterize the interaction between the proteins, and a model structure of the complex was obtained by molecular docking. The electrochemical observations point to the modulation of the NorC reduction potential by the presence of NorB, tuning its ability to receive electrons from cytochrome c₅₅₂.

马立诺杆菌碳氢化合物一氧化氮还原酶c NOR是一个完整的膜蛋白，由两个具有不同作用的亚基组成，NorC（电子转移）和NorB（催化）从可溶性细胞色素c ₅₅₂接收电子并将氮氧化物还原为一氧化二氮。反硝化途径。带有c型血红素的NorC的溶剂暴露域与它的生理电子供体细胞色素c ₅₅₂异源产生。对这两种蛋白质进行了光谱表征，并显示出与天然蛋白质相似，二者均为低旋和Met-His配位，NorC的可溶性结构域呈现高旋血红素的一些其他特征，这与较高的血红素一致。血红素的溶剂可及性和蛋氨酸轴向配体的配位较弱。两种蛋白质之间的电子转移复合物的化学计量比为1：1，解离常数的上限估计为¹1 H NMR滴定为1.2±0.4μM。使用电化学技术表征蛋白质之间的相互作用，并通过分子对接获得复合物的模型结构。电化学观察表明，通过NorB的存在来调节NorC还原电势，从而调节其从细胞色素c ₅₅₂接收电子的能力。