| Red contour lines indicate net negative electrostatic potential; blue lines net positive potential. The enzyme is shown as a homodimer (green ribbons) and two active sites (one in each subunit) can be seen at the top left and bottom right of the figure where a significant concentration of positive electrostatic potential is indicated by the blue contour lines curving away from the protein surface. The negative potential elsewhere on the protein will repel the negatively charged superoxide substrate (O2-·) and prevent non-productive binding, while the positive potential in the active site will attract it. Graphic kindly provided by Barry Honig and Emil Alexov. |
