8). The Selleck C646 column was developed with 500 ml of a 0-1.0 M NaCl linear gradient. Each

10 ml fraction was assayed for CO dehydrogenase activity by monitoring the CO-dependent reduction of methyl viologen as previously described [42]. The pooled fractions Selleck URMC-099 from the peak with the highest specific activity were concentrated 10-fold with a Vivacell 70 protein concentrator equipped with a 10-kDa cut off membrane (Sartorius Group, Göttingen, Germany). A 1.0 M solution of (NH4)2SO4 contained in 50 mM MOPS (pH 6.8) was added to the concentrated protein solution to final concentration of 900 mM and loaded onto a Phenyl-Sepharose FF (low sub) column (20-ml bed volume) equilibrated with 50 mM MOPS (pH 6.8) containing 1.0 M (NH4)2SO4. The column was developed with 100 ml of a 1.0-0.0 M (NH4)2SO4 decreasing linear gradient. Fractions from the peak of CO dehydrogenase activity were pooled and concentrated followed by addition of a volume of 50 mM learn more MOPS (pH 6.8) to lower the (NH4)2SO4 concentration to below 100 mM and then loaded on a HiTrap Q-Sepharose HP column (5 ml bed

volume) equilibrated with 50 mM MOPS buffer (pH 6.8). The column was developed with 50 ml of a 0-1.0 M NaCl linear gradient. The peak containing CO dehydrogenase activity that eluted at approximately 0.3 M NaCl was collected and stored at -80°C until use. Purification of ferredoxin All purification steps and biochemical assays were performed anaerobically in the anaerobic chamber. Ferredoxin was assayed by the ability to couple Terminal deoxynucleotidyl transferase CO oxidation by CdhAE to the reduction of metronidazole followed by the decrease in A 320 (ε320 = 9300 M-1 cm-1) similar to that described previously [27]. One unit of activity was the amount that reduced 1 μmol of metronidazole/min. The reaction mixture (100 μl) contained 100 μM metronidazole and 1-3 μg CdhAE in 50 mM Tris buffer (pH 8.0) to which 1-10 μl of the

column fraction was added. The reaction was contained in an anaerobic cuvette flushed with 100% CO. The soluble fraction of cell extract from acetate-grown M. acetivorans was loaded onto a Q-sepharose FF column (20 ml bed volume) equilibrated with 50 mM MOPS (pH 6.8) containing 10% (v/v) ethylene glycol. The column was developed with 200 ml of a 0-1.0 M linear NaCl gradient. The fraction with the highest activity was then diluted 10-fold with 50 mM MOPS (pH 6.8) containing 10% (v/v) ethylene glycol. The solution was loaded on a Mono Q column (1.7 ml bed volume) to which 10 ml of a 0-1.0 M NaCl linear gradient was applied. The fraction containing ferredoxin that eluted at 600 mM NaCl was loaded on a Sephadex G-75 gel filtration column (100 ml bed volume) and developed with 50 mM MOPS (pH 6.8) containing 10% (v/v) ethylene glycol and 150 mM NaCl. The peak containing the purified ferredoxin was concentrated to A402 > 0.2 with a Vivacell 70 protein concentrator equipped with a 5-kDa cutoff membrane and stored at -80°C until use.