Substrate interaction at an iron-sulfur face of the FeMo-cofactor during nitrogenase catalysis

被引:120
作者
Barney, BM
Igarashi, RY
Dos Santos, PC
Dean, DR [1 ]
Seefeldt, LC
机构
[1] Virginia Tech, Dept Biochem, Blacksburg, VA 24061 USA
[2] Utah State Univ, Dept Chem & Biochem, Logan, UT 84322 USA
关键词
D O I
10.1074/jbc.M410247200
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
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.
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页码:53621 / 53624
页数:4
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