Fig. 2.

The structure of NrtA. (A) Stereo ribbon representation of the NrtA crystal structure colored blue to red as the chain extends from the N terminus to the C terminus. NrtA consists of two α/β domains arranged with a C-clamp shape, with nitrate, depicted as spheres, bound in the cleft between the two domains. The view is of the front of the C-clamp, which opens to the nitrate-binding cleft. (B) Electrostatic surface potential of the front and back of the NrtA structure, with positive and negative charge shown in blue and red, respectively.