Type 2 Cu2+ in pMMO from Methylomicrobium album BG8

EPR spectra were obtained for the type 2 Cu2+ Site in particulate methane monooxygenase (pMMO) from Methylomicrobium album BG8 grown on (KNO3)-N-15 and Cu-63(NO3)(2). The concentration of the type 2 Cu2+ signal was similar to 200 mu M per 25 mg/ml protein in packed cells and membrane fractions, a concentration that is consistent with its attribution to pMMO, and the EPR parameters were consistent with electron paramagnetic resonance (EPR) parameters previously assigned to pMMO. The superhyperfine structure due to nitrogen is better resolved because I = 1/2 for N-15 whereas I = 1 for N-14 and A(N-15)/A(N-14) = 1.4. Under these conditions, superhyperfine structure is resolved in the g(parallel to) region of the X-band spectrum. At low microwave frequency (S-band) the resolution of the nitrogen superhyperfine structure improves. Signals are attributed to type 2 Cu2+ which cupric ion is bound to four (less likely three) nitrogen donor atoms.