Table 4. Structural Differences in Angstroms Relative to CAT-5 (no sixth iron ligand) Averaged over All Four Subunits.

	CAT-NH3	CAT-NO
heme Fe and N atoms	0.1 ± 0.01	0.1 ± 0.01
proximal side of the heme
Tyr357 Oη	0.11 ± 0.02	0.14 ± 0.04
distal side of the heme
His74 Nδ1/Nε2	0.12 ± 0.06	0.14 ± 0.06
Asn147 Oδ1/Nδ2	0.12 ± 0.07	0.16 ± 0.08
Phe160 Cζ	0.15 ± 0.03	0.13 ± 0.07
total rms differencea	0.34 ± 0.04	0.37 ± 0.05

^aThe structures were superimposed by a least-squares fit (Xfit(41)).