Nitrosyl-heme structures of Bacillus subtilis nitric oxide synthase have implications for understanding substrate oxidation
Nitrosyl-heme structures of Bacillus subtilis nitric oxide synthase have implications for understanding substrate oxidation
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DOI：
10.1021/bi0518848
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发表时间：
2006-02-28
期刊：
影响因子：
2.9
通讯作者：
Crane, BR
中科院分区：
文献类型：
--
作者：
Pant, K;Crane, BR
来自枯草杆菌（bsNOS）的原核一氧化氮合酶（NOS）的亚硝酰-血红素复合物的晶体结构揭示了与底物L-精氨酸（L-Arg）相比，在中间体N-ω-羟基-L-精氨酸（NOHA）存在下活性位点氢键的变化。与bsNOS血红素口袋中Val至Ile残基取代相关，具有L-Arg和NOHA两者的Fe（II）-NO复合物比哺乳动物eNOS的Fe（II）-NO、L-Arg复合物更弯曲[Li，H.，拉曼，C.美国，Martasek，P.，马斯特斯，B。S.美国，和Poulos，T. L.（2001）Biochemistry 40，5399-5406]。Fe（III）-NO与NOHA的复合物的结构显示出几乎线性的亚硝酰基，并且在一个亚基中，结合NOHA的部分亚硝化。在Fe（II）-NO复合物中，质子化的NOHA N-ω原子与血红素配位的NO氮形成短氢键，但活性位点的水分子与远端NO氧不在氢键范围内。相比之下，L-Arg胍与NO原子的相互作用更弱且相等，并且活性位点水分子氢键结合到远端NO氧。这两种底物与亚硝酰基的氢键结合的差异表明，NOHA提供的相互作用可以优先稳定NOS催化的第二步中的亲电过氧血红素中间体。
The crystal structures of nitrosyl-heme complexes of a prokaryotic nitric oxide synthase (NOS) from Bacillus subtilis (bsNOS) reveal changes in active-site hydrogen bonding in the presence of the intermediate N-omega-hydroxy-L-arginine (NOHA) compared to the substrate L-arginine (L-Arg). Correlating with a Val-to-Ile residue substitution in the bsNOS heme pocket, the Fe(II)-NO complex with both L-Arg and NOHA is more bent than the Fe(II)-NO, L-Arg complex of mammalian eNOS [Li, H., Raman, C. S., Martasek, P., Masters, B. S. S., and Poulos, T. L. (2001) Biochemistry 40, 5399-5406]. Structures of the Fe(III)-NO complex with NOHA show a nearly linear nitrosyl group, and in one subunit, partial nitrosation of bound NOHA. In the Fe(II)-NO complexes, the protonated NOHA N-omega atom forms a short hydrogen bond with the heme-coordinated NO nitrogen, but active-site water molecules are out of hydrogen bonding range with the distal NO oxygen. In contrast, the L-Arg guanidinium interacts more weakly and equally with both NO atoms, and an active-site water molecule hydrogen bonds to the distal NO oxygen. This difference in hydrogen bonding to the nitrosyl group by the two substrates indicates that interactions provided by NOHA may preferentially stabilize an electrophilic peroxo-heme intermediate in the second step of NOS catalysis.