“Murano glass" rendition of the heme domain of FixL
Ralph Jimenez (JILA, UCB)

Computer model built with Visual Molecular Dynamics from structure coordinates
The FixL oxygen sensor of the rhizobial bacterium Bradyrhizobium Japonicum is part of a signal transduction chain that regulates transcription of nitrogen fixation enzymes. The heme domain, shown here, binds oxygen at the heme (the planar cofactor rendered in chrome) and the side-chains adjacent to the heme (also in chrome) rearrange and cause conformational changes in the FG loop (in red glass), which transmits this signal "downstream." The FG loop may therefore be considered a switch, whose conformation and flexibility signal the presence of oxygen in the environment.

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