Table 2. Refinement statistics.

Rwork, %	19.6
Rfree,* %	24.0
No. of nonhydrogen atoms
Protein	5,964
Water	569
Heme	86
rms deviation from ideality
Bond lengths, Å	0.0058
Bond angles, °	1.35
Estimated coordinate error (Luzzati), Å	0.22
Average B-factor	20.4
Protein, Å2	19.3
Water	25.2
Heme	14.9
Disallowed, %	0.3

^*R = Σ||F_o| – |F_c||/Σ|F_o|, where F_o and F_c are the observed and calculated structure factors amplitudes. R_free is calculated by using 5% of the total reflections