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Uncoupling binding of substrate CO from turnover by vanadium nitrogenase

  • Author(s): Lee, CC
  • Fay, AW
  • Weng, TC
  • Krest, CM
  • Hedman, B
  • Hodgson, KO
  • Hu, Y
  • Ribbe, MW
  • et al.
Abstract

Biocatalysis by nitrogenase, particularly the reduction of N2and CO by this enzyme, has tremendous significance in environmentand energy-related areas. Elucidation of the detailed mechanism of nitrogenase has been hampered by the inability to trap substrates or intermediates in a well-defined state. Here, we report the capture of substrate CO on the resting-state vanadium-nitrogenase in a catalytically competent conformation. The close resemblance of this active CO-bound conformation to the recently described structure of CO-inhibited molybdenum-nitrogenase points to the mechanistic relevance of sulfur displacement to the activation of iron sites in the cofactor for CO binding. Moreover, the ability of vanadium-nitrogenase to bind substrate in the resting-state uncouples substrate binding from subsequent turnover, providing a platform for generation of defined intermediate(s) of both CO and N2reduction.

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