Substrate interaction at an iron-sulfur face of the FeMo-cofactor during nitrogenase catalysis
Substrate interaction at an iron-sulfur face of the FeMo-cofactor during nitrogenase catalysis
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DOI：
10.1074/jbc.m410247200
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发表时间：
2004-12-17
影响因子：
4.8
通讯作者：
Seefeldt, LC
中科院分区：
文献类型：
--
作者：
Barney, BM;Igarashi, RY;Seefeldt, LC
固氮酶催化生物固氮，将N-2还原为2NH（3）。最近，非生理性炔底物（炔丙醇，HC相当于C-CH 2 OH）的结合位点被定位于由MoFe蛋白氨基酸α-70（瓦尔）接近的FeMo-辅因子的特定Fe-S面。在这里，我们提供的证据表明，较小的炔底物乙炔（HC相当于CH），生理底物二氮，其半还原形式肼（H2 N-NH 2）与FeMo-辅因子的相同Fe-S面相互作用。肼是野生型（α-70（瓦尔））MoFe蛋白的相对较差的底物。用具有较小侧链的氨基酸（丙氨酸）取代α-70（瓦尔）残基显著增强肼还原活性。相反，用具有较大侧链的氨基酸（异亮氨酸）取代α-70（瓦尔）显著降低了MoFe蛋白还原二氮、肼或乙炔的能力。
Nitrogenase catalyzes biological dinitrogen fixation, the reduction of N-2 to 2NH(3). Recently, the binding site for a non-physiological alkyne substrate (propargyl alcohol, HCequivalent toC-CH2OH) was localized to a specific Fe-S face of the FeMo-cofactor approached by the MoFe protein amino acid alpha-70(Val). Here we provide evidence to indicate that the smaller alkyne substrate acetylene (HCequivalent toCH), the physiological substrate dinitrogen, and its semi-reduced form hydrazine (H2N-NH2) interact with the same Fe-S face of the FeMo-cofactor. Hydrazine is a relatively poor substrate for the wild-type (alpha-70(Val)) MoFe protein. Substitution of the alpha-70(Val) residue by an amino acid having a smaller side chain (alanine) dramatically enhanced hydrazine reduction activity. Conversely, substitution of alpha-70(Val) by an amino acid having a larger side chain (isoleucine) significantly lowered the capacity of the MoFe protein to reduce dinitrogen, hydrazine, or acetylene.