15. Lanzilotta WN, Ryle MJ, Seefeldt LC (1995) Nucleotide hydrolysis and protein
conformational changes in Azotobacter vinelandii nitrogenase iron protein: defining the
function of aspartate 129. Biochemistry 34(34):10713–10723
16. Watt GD, Reddy KRN (1994) Formation of an all ferrous Fe 4 S 4 cluster in the iron protein
component of Azotobacter vinelandii nitrogenase. J. Inorg. Biochem 53:281–294
17. Guo M, Sulc F, Ribbe MW, Farmer PJ, Burgess BK (2002) Direct assessment of the
reduction potential of the [4Fe-4S]
1+/0 couple of the Fe protein from Azotobacter vinelandii.
J Am Chem Soc 124(41):12100–12101
18. Kim J, Rees DC (1992) Crystallographic structure and functional implications of the
nitrogenase molybdenum-iron protein from Azotobacter vinelandii. Nature 360(6404):553–
560
19. Chan MK, Kim J, Rees DC (1993) The nitrogenase FeMo-cofactor and P-cluster pair: 2.2 Å
resolution structures. Science 260(5109):792–794
20. Peters JW, Stowell MH, Soltis SM, Finnegan MG, Johnson MK, Rees DC (1997)
Redox-dependent structural changes in the nitrogenase P-cluster. Biochemistry 36(6):1181–
1187
21. Sørlie M, Christiansen J, Lemon BJ, Peters JW, Dean DR, Hales BJ (2001) Mechanistic
features and structure of the nitrogenase a-Gln195 MoFe protein. Biochemistry 40(6):1540–
1549
22. Einsle O, Tezcan FA, Andrade SL et al (2002) Nitrogenase MoFe-protein at 1.16 Å
resolution: a central ligand in the FeMo-cofactor. Science 297(5587):1696–1700
23. Schmid B, Ribbe MW, Einsle O et al (2002) Structure of a cofactor-deficient nitrogenase
MoFe protein. Science 296(5566):352–356
24. Tezcan FA, Kaiser JT, Mustafi D, Walton MY, Howard JB, Rees DC (2005) Nitrogenase
complexes: multiple docking sites for a nucleotide switch protein. Science 309(5739):1377–
1380
25. Schindelin H, Kisker C, Schlessman JL, Howard JB, Rees DC (1997) Structure of ADP Á
AIF4–stabilized nitrogenase complex and its implications for signal transduction. Nature 387
(6631):370–376
26. Schmid B, Einsle O, Chiu HJ et al (2002) Biochemical and structural characterization of the
cross-linked complex of nitrogenase: comparison to the ADP Á AIF4–stabilized structure.
Biochemistry 41(52):15557–15565
27. Surerus KK, Hendrich MP, Christie PD, Rottgardt D, Orme-Johnson WH, Münck E (1992)
Mössbauer and integer-spin EPR of the oxidized P-clusters of nitrogenase: P
OX is a
non-Kramers system with a nearly degenerate ground doublet. J Am Chem Soc 114
(22):8579–8590
28. Zimmermann R, Münck E, Brill WJ, et al (1978) Nitrogenase X: Mössbauer and EPR
studies on reversibly oxidized MoFe protein from Azotobacter vinelandii OP. Nature of the
iron centers. Biochim Biophys Acta 537(2):185–207
29. Pierik AJ, Wassink H, Haaker H, Hagen WR (1993) Redox properties and EPR
spectroscopy of the P clusters of Azotobacter vinelandii MoFe protein. Eur J Biochem
212(1):51–61
30. Keable SM, Zadvornyy OA, Johnson LE et al (2018) Structural characterization of the P
1+
intermediate state of the P-cluster of nitrogenase. J Biol Chem 293(25):9629–9635
31. Rutledge HL, Rittle J, Williamson LM, Xu WA, Gagnon DM, Tezcan FA (2019)
Redox-dependent metastability of the nitrogenase P-cluster. J Am Chem Soc 141
(25):10091–10098
32. Spatzal T, Aksoyoglu M, Zhang L et al (2011) Evidence for interstitial carbon in nitrogenase
FeMo cofactor. Science 334(6058):940
33. Burgess BK (1990) The iron-molybdenum cofactor of nitrogenase. Chem Rev 90:1377–
1406
34. Shah VK, Brill WJ (1977) Isolation of an iron-molybdenum cofactor from nitrogenase. Proc
Natl Acad Sci U S A 74(8):3249–3253
180
C.-C. Lee et al.
conformational changes in Azotobacter vinelandii nitrogenase iron protein: defining the
function of aspartate 129. Biochemistry 34(34):10713–10723
16. Watt GD, Reddy KRN (1994) Formation of an all ferrous Fe 4 S 4 cluster in the iron protein
component of Azotobacter vinelandii nitrogenase. J. Inorg. Biochem 53:281–294
17. Guo M, Sulc F, Ribbe MW, Farmer PJ, Burgess BK (2002) Direct assessment of the
reduction potential of the [4Fe-4S]
1+/0 couple of the Fe protein from Azotobacter vinelandii.
J Am Chem Soc 124(41):12100–12101
18. Kim J, Rees DC (1992) Crystallographic structure and functional implications of the
nitrogenase molybdenum-iron protein from Azotobacter vinelandii. Nature 360(6404):553–
560
19. Chan MK, Kim J, Rees DC (1993) The nitrogenase FeMo-cofactor and P-cluster pair: 2.2 Å
resolution structures. Science 260(5109):792–794
20. Peters JW, Stowell MH, Soltis SM, Finnegan MG, Johnson MK, Rees DC (1997)
Redox-dependent structural changes in the nitrogenase P-cluster. Biochemistry 36(6):1181–
1187
21. Sørlie M, Christiansen J, Lemon BJ, Peters JW, Dean DR, Hales BJ (2001) Mechanistic
features and structure of the nitrogenase a-Gln195 MoFe protein. Biochemistry 40(6):1540–
1549
22. Einsle O, Tezcan FA, Andrade SL et al (2002) Nitrogenase MoFe-protein at 1.16 Å
resolution: a central ligand in the FeMo-cofactor. Science 297(5587):1696–1700
23. Schmid B, Ribbe MW, Einsle O et al (2002) Structure of a cofactor-deficient nitrogenase
MoFe protein. Science 296(5566):352–356
24. Tezcan FA, Kaiser JT, Mustafi D, Walton MY, Howard JB, Rees DC (2005) Nitrogenase
complexes: multiple docking sites for a nucleotide switch protein. Science 309(5739):1377–
1380
25. Schindelin H, Kisker C, Schlessman JL, Howard JB, Rees DC (1997) Structure of ADP Á
AIF4–stabilized nitrogenase complex and its implications for signal transduction. Nature 387
(6631):370–376
26. Schmid B, Einsle O, Chiu HJ et al (2002) Biochemical and structural characterization of the
cross-linked complex of nitrogenase: comparison to the ADP Á AIF4–stabilized structure.
Biochemistry 41(52):15557–15565
27. Surerus KK, Hendrich MP, Christie PD, Rottgardt D, Orme-Johnson WH, Münck E (1992)
Mössbauer and integer-spin EPR of the oxidized P-clusters of nitrogenase: P
OX is a
non-Kramers system with a nearly degenerate ground doublet. J Am Chem Soc 114
(22):8579–8590
28. Zimmermann R, Münck E, Brill WJ, et al (1978) Nitrogenase X: Mössbauer and EPR
studies on reversibly oxidized MoFe protein from Azotobacter vinelandii OP. Nature of the
iron centers. Biochim Biophys Acta 537(2):185–207
29. Pierik AJ, Wassink H, Haaker H, Hagen WR (1993) Redox properties and EPR
spectroscopy of the P clusters of Azotobacter vinelandii MoFe protein. Eur J Biochem
212(1):51–61
30. Keable SM, Zadvornyy OA, Johnson LE et al (2018) Structural characterization of the P
1+
intermediate state of the P-cluster of nitrogenase. J Biol Chem 293(25):9629–9635
31. Rutledge HL, Rittle J, Williamson LM, Xu WA, Gagnon DM, Tezcan FA (2019)
Redox-dependent metastability of the nitrogenase P-cluster. J Am Chem Soc 141
(25):10091–10098
32. Spatzal T, Aksoyoglu M, Zhang L et al (2011) Evidence for interstitial carbon in nitrogenase
FeMo cofactor. Science 334(6058):940
33. Burgess BK (1990) The iron-molybdenum cofactor of nitrogenase. Chem Rev 90:1377–
1406
34. Shah VK, Brill WJ (1977) Isolation of an iron-molybdenum cofactor from nitrogenase. Proc
Natl Acad Sci U S A 74(8):3249–3253
180
C.-C. Lee et al.