Effect of methanobactin on the activity and electron paramagnetic resonance spectra of the membrane-associated methane monooxygenase in Methylococcus capsulatus Bath

1 Department of Biochemistry, Biophysics and Molecular Biology, 4164 Molecular Biology Building, Iowa State University, Ames, IA 50011-3211, USA 2 Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA 3 Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, MI 48109-2125, USA 4 Department of Chemistry, University of Wisconsin-Eau Claire, Eau Claire, WI 54702, USA Correspondence Alan A. DiSpirito aland{at}iastate.edu Improvements in the purification of methanobactin (mb) from either Methylosinus trichosporium OB3b T or Methylococcus capsulatus Bath resulted in preparations that stimulated methane-oxidation activity in both whole-cell and cell-free fractions of Methylococcus capsulatus Bath expressing the membrane-associated methane monooxygenase (pMMO). By using washed membrane factions with pMMO activities in the 290 nmol propylene oxidized min –1 (mg protein) –1 range, activities approaching 400 nmol propylene oxidized min –1 (mg protein) –1 were commonly observed following addition of copper-containing mb (Cu–mb), which represented 50–75 % of the total whole-cell activity. The stimulation of methane-oxidation activity by Cu–mb was similar to or greater than that observed with equimolar concentrations of Cu(II), without the inhibitory effects observed with high copper concentrations. Stimulation of pMMO activity was not observed with copper-free mb, nor was it observed when the copper-to-mb ratio was