The Production of Ammonia by Multiheme Cytochromes c - The Metal-Driven Biogeochemistry of Gaseous Compounds in the Environment - page 224

Figure 8 The substrate entry (blue) and product exit (red) channels of cytochrome c nitrite
reductase (NrfA). Apart from the entry channel leading from the protein surface to the catalytic
site heme 1, a second exit channel exists that reaches the protein surface on the opposite side of the
molecule. The whole channel is colored according to the electrostatic surface potential; blue for a
positive and red for a negative potential. Modified from [ 58 ].
membrane-spanning helix and a globular cytochrome c domain situated at the
outside of the bacterial membrane.
Within their enzymic contexts, NapC and NrfH donate electrons, either directly
or indirectly, to periplasmic nitrate reductase (NapA) or NrfA, respectively.
Another member of this family (CymA) from Shewanella species such as
S. oneidensis was shown to serve as an electron hub within several respiratory
chains that terminate with, for example, periplasmic nitrate reductase (NapA),
cytochrome c nitrite reductase (NrfA) or cytochrome c fumarate reductase
(Table 1 , enzyme class 2.3). From the crystal structure of the D. vulgaris