TABLE 3.
EPR spectroscopic properties of NeHAO, KsHOX, and KsHDH
EPR species are numbered according to Ref. 15 with our refinement.
| Protein EPR species (iron/monomer)a | gxyz values | Comment/Assignment |
|---|---|---|
| NeHAOb | ||
| 1 (1) | 1.20; 2.26; 3.03 | Uncoupled heme 1 |
| 2 (3) | 1.35; 2.19; 3.11 (3.09)c | Uncoupled hemes 7 and 8; includes the easily reducible heme 2 |
| 3 (2) | 1.27; 2.28; 3.06 | Coupled hemes 3 and 5 |
| 4 (2) | 8 | Coupled hemes 6 and 4 (P460); only observed in parallel mode EPR |
| KsHOX | ||
| 1 (1) | 1.452; 2.305; 2.955 | Heme 1; g values become 1.452, 2.260, and 2.980 after NH2OH incubation |
| 2a (1) | 1.41; 2.145; 3.1412 | Reduced after NH2OH incubation; heme 2 |
| 2b (2) | 1.41, 2.217, 2.955 | Uncoupled hemes 7 and 8; g values become 1.37, 2.217, and 2.980 after NH2OH incubation |
| 3 (2) | 1.40; 2.18; 3.247 | Coupled hemes 3 and 5 (Euler angles: 45, −180, and 135°); after NH2OH incubation, each heme reduces by 60%, gz changes to 3.265, and the exchange splitting increases from 0.031 to 0.035 cm−1 |
| 4 (2) | NDd | |
| 5 (minor) | 6.07; 5.81; 1.98 | High spin heme, but amount is preparation-dependent (0.03–0.14/monomer; the higher value shown in Figs. 8 (A and B) and 9A |
| KsHDH | ||
| 1 (1) | 1.6; 2.05; 3.14 | Uncoupled heme (heme 1) with broad resonances that sharpen and shift (gx,y,z = 1.51, 2.256, 3.10) upon reduction by hydrazine |
| 2a (1) (3.8%) (6.7%) (6.1%) | 1.772; 2.06; 2.579 | Heme 2; N2H4-reducible; same heme in slightly different environments |
| 2b (2) | 1.772; 2.06; 2.543 | |
| 1.772; 2.06; 2.497 | ||
| 1.5; 2.3; 3.0 | Coupled hemes 7 and 8 (Euler angles: 45, 180, and 87°); no reduction by hydrazine, but gz changes to 3.05; the exchange splitting is 0.035 cm−1 | |
| 3 (2) | 1.5; 2.3; 3.0 | Coupled hemes 3 and 5 (Euler angles: 45, −180, and 135°); reduction by hydrazine (70%), and gz changes to 3.04; the exchange splitting is 0.074 cm−1 and 0.087 cm−1 after reduction |
| 4 (2) | ND | |
| 5 (minor) | 6.0; 6.0; 2.0 | Minor high spin heme (<0.02/monomer) |
| 6 (minor) | 2.009 | Possible tyrosine radical coupled to heme 4 |
a In column 1, numbers in parentheses indicate the integral number of spins, and percentage values represent the percentage of the total of integrated spins.
b Data from Hendrich et al. (15).
c In parentheses, gz after 1-electron reduction.
d ND, not determined. Signal accounting for hemes 6 and 4, which only would be observed in parallel mode EPR.