Extended Data Fig. 2: CryoEM and activity analyses of FeSII-nitrogenase samples that are O2-exposed or under reduced/anaerobic conditions.
From: Structural basis for the conformational protection of nitrogenase from O2
a, Four denoised micrographs from the O2-exposed sample (top) and 50 class averages obtained from 2-D classification (bottom) illustrating the presence of the 2:2:1 complex and extended polymers. b, Four denoised micrographs from the anaerobic sample (top) and 50 class averages from 2-D classification (bottom) indicating lack of 2:2:1 complexes (or polymers) and that most classes contain free MoFeP and FeP. c, Relative catalytic activities of MoFeP and FeP samples that have been prepared using the cryoEM sample preparation conditions, as monitored by acetylene reduction experiments. In these experiments, FeP and MoFeP mixtures were made using the cryoEM sample preparation conditions in the presence or absence of FeSII and with or without O2 exposure for 2 min. After this treatment, FeP and MoFeP mixtures were tested for acetylene reduction activity under anaerobic conditions after being transferred into a solution containing DT, MgATP and an enzymatic ATP regeneration system (see Methods). Blue dots: MoFeP + FeP + FeSII – O2. Green dots: MoFeP + FeP + FeSII + O2. Red dots: MoFeP + FeP – FeSII + O2. Error bars correspond to standard deviation from the mean of three biological replicates.
