Cutruzzolà F, Arese M, Grasso S, Bellelli A, Brunori M
Dipartimento di Scienze Biochimiche A. Rossi Fanelli and Centro di Biologia Molecolare del CNR, Università di Roma La Sapienza, Italy.
FEBS Lett. 1997 Jul 28;412(2):365-9. doi: 10.1016/s0014-5793(97)00583-8.
In Pseudomonas aeruginosa, conversion of nitrite to NO in dissimilatory denitrification is catalyzed by the enzyme nitrite reductase (NiR), a homodimer containing a covalently bound c heme and a d1 heme per subunit. We report the purification and characterization of the first single mutant of P. aeruginosa cd1 NiR in which Tyr10 has been replaced by Phe; this amino acid was chosen as a possibly important residue in the catalytic mechanism of this enzyme based on the proposal (Fulop, V., Moir, J.W.B., Ferguson, S.J. and Hajdu, J. (1995) Cell 81, 369-377) that the topologically homologous Tyr25 plays a crucial role in controlling the activity of the cd1 NiR from Thiosphaera pantotropha. Our results show that in P. aeruginosa NiR substitution of Tyr10 with Phe has no effect on the activity, optical spectroscopy and electron transfer kinetics of the enzyme, indicating that distal coordination of the Fe3+ of the d1 heme is provided by different side-chains in different species.
在铜绿假单胞菌中，异化反硝化过程中亚硝酸盐向一氧化氮的转化由亚硝酸还原酶（NiR）催化，该酶为同型二聚体，每个亚基含有一个共价结合的c型血红素和一个d1型血红素。我们报道了铜绿假单胞菌cd1 NiR首个单突变体的纯化及特性，其中Tyr10被Phe取代；基于Fulop等人（1995年，《细胞》81卷，369 - 377页）的提议，即拓扑结构同源的Tyr25在控制泛养硫球菌cd1 NiR的活性中起关键作用，选择该氨基酸作为该酶催化机制中可能重要的残基。我们的结果表明，在铜绿假单胞菌NiR中用Phe取代Tyr10对该酶的活性、光谱学和电子转移动力学没有影响，这表明d1型血红素中Fe3 +的远端配位在不同物种中由不同的侧链提供。
