title: Uncoupling binding of substrate CO from turnover by vanadium nitrogenase.
abstract: Biocatalysis by nitrogenase, particularly the reduction of N2 and CO by this enzyme, has tremendous significance in environment- and 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 N2 reduction.
authors.affiliation: Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697-3900;
authors.forename: Chi Chung
authors.initials: CC
authors.lastname: Lee
authors.affiliation: Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697-3900;
authors.forename: Aaron W
authors.initials: AW
authors.lastname: Fay
authors.affiliation: Stanford Synchrotron Radiation Lightsource, Stanford Linear Accelerator Center (SLAC) National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025; Center for High Pressure Science & Technology Advanced Research, Shanghai 201203, China;
authors.forename: Tsu-Chien
authors.initials: TC
authors.lastname: Weng
authors.affiliation: Stanford Synchrotron Radiation Lightsource, Stanford Linear Accelerator Center (SLAC) National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025;
authors.forename: Courtney M
authors.initials: CM
authors.lastname: Krest
authors.affiliation: Stanford Synchrotron Radiation Lightsource, Stanford Linear Accelerator Center (SLAC) National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025;
authors.forename: Britt
authors.initials: B
authors.lastname: Hedman
authors.affiliation: Stanford Synchrotron Radiation Lightsource, Stanford Linear Accelerator Center (SLAC) National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025; Department of Chemistry, Stanford University, Stanford, CA 94305; hodgsonk@stanford.edu yilinh@uci.edu mribbe@uci.edu.
authors.forename: Keith O
authors.initials: KO
authors.lastname: Hodgson
authors.affiliation: Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697-3900; hodgsonk@stanford.edu yilinh@uci.edu mribbe@uci.edu.
authors.forename: Yilin
authors.initials: Y
authors.lastname: Hu
authors.affiliation: Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697-3900; Department of Chemistry, University of California, Irvine, CA 92697-2025 hodgsonk@stanford.edu yilinh@uci.edu mribbe@uci.edu.
authors.forename: Markus W
authors.initials: MW
authors.lastname: Ribbe
mesh_terms: D002248:Carbon Monoxide / Q000737:chemistry / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D008958:Models, Molecular; D009591:Nitrogenase / Q000737:chemistry / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D002248:Carbon Monoxide; D009591:Nitrogenase
keywords: carbon monoxide; nitrogenase; substrate binding; turnover; vanadium