NN22 + 16MgATP+ 16MgATP2-2- + 8e + 8e-- + 8H + 8H++ → →

2NH2NH33 + 16MgADP + 16MgADP- - + 16H + 16H22POPO44-- + H + H22

Complex of the nitrogenase proteins stabilized by ADP-AIF4−

Howard J. B., Rees D. C. PNAS 2006;103:17088-17093

©2006 by National Academy of Sciences

Ball-and-stick representation of the nitrogenase metalloclusters

Howard J. B., Rees D. C. PNAS 2006;103:17088-17093

©2006 by National Academy of Sciences

A view of the FeMo cofactor highlighting Fe atoms 2, 3, 6, and 7 (numbering from Protein Data Bank ID code 1M1N), along with MoFe protein amino acids ligands (α-275Cys and α-442His) and

the side chains of α-195His and α-70Val

Barney B. M. et.al. PNAS 2006;103:17113-17118

©2006 by National Academy of Sciences

N NMH+

N NHM N NHM+H+

N NH2M+

N NH2M+2

H+

N NH3M+2

NH3

NM+2

2+

NM+2NM+3

NH3

1. 3H+, 6 e-

2. N2

Chatt-Type Mechanism for Single Site Catalysis

N2 + 6H+ + 6e- → 2NH3

http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1859894

Proc Natl Acad Sci U S A. 2006 November 14; 103(46): 17088–17093.

How many metals does it take to fix N2? A mechanistic overview of biological nitrogen fixation

James B. Howard*† and Douglas C. Rees†‡

*Department of Biochemistry, University of Minnesota, Minneapolis, MN 55455; and

‡Division of Chemistry and Chemical Engineering, 114-96, Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA 91125

Mo

N

NN 2

Mo(VI) Terminal NitridoMo(III) Terminal ImidoMo(6), N(3x3), total = 15 Mo(6), Nimido(9), Nnitrido(3), total = 18

Mo N

NN

N

N2, 1 atm2

238K

Science, 268, 861-863

Kit Cummins Lab at MIT, 1995

Mo

N

NN

MoN(R)Ar

N(R)Ar

Ar(R)N

Mo(III) Terminal ImidoMo(6), N(3x3), total = 15

Science, 268, 861-863

Kit Cummins Lab at MIT, 1995

MoN(R)Ar

N(R)Ar

Ar(R)N N2, 1 atm

238 KMo

N(R)Ar

N(R)ArAr(R)N

N

N

Mo(N(R)Ar)3

Mo

N(R)Ar

N(R)ArAr(R)N

N

N

Mo

N(R)Ar

N(R)ArAr(R)N

purple

Mo

N(R)Ar

N(R)ArAr(R)N

N

N

Mo

N(R)Ar

N(R)ArAr(R)N

Mo

N(R)Ar

N(R)ArAr(R)N

N2

1

1

Science, 331, 1049

Science, 331, 1049