Mercury Toxicity on Sodium Pump and Organoseleniums Intervention: A Paradox
Figure 1
Reaction cycle. The minimal steps in the catalysis-transport cycle of sodium pump are shown schematically. Black arrows indicate the normal, clockwise direction of the reaction sequence. Oxygen isotope (red) exchange may occur in the reversible step colored red. The cycle represents the sidedness, as well as repetition, of the reactions. For example, the 3 Na+ (blue) that displace 2 K+ (green) intracellularly are subsequently displaced by 2 K+ extracellularly, generating the inward Na+ (larger) and outward K+ (smaller) gradients indicated by wedge shapes. A circle and a square symbolize the limiting protein conformations (E1 and E2, resp.) with enclosed ions indicating occlusion. Different colors denote ATP acting as an effector (gray) or substrate (black) [9].
