Figure 1. Active center of nitrogenase. The iron-molybdenum cofactor consists of molybdenum (orange), iron (gray), and sulfur (yellow) with the central nitrogen atom (blue). The cofactor is connected to the protein via two amino acids that affix the metal center only at its ends. In addition, an organic molecule, homocitrate, is linked to the center (bottom right). (Model: Oliver Einsle, Goettingen, Germany.)
|
Figure 2. Symbiotic nitrogen fixation. Left: root tubercles (Christine Hallmann, Goettingen). Right: cross-section of a root tubercle filled with N 2-fixing bacteroids. (Photograph: Anne Kemmling, Goettingen, Germany.)
|