Sandbox Reserved 1069: Difference between revisions

It is believed that the energy for TMD conformation change comes from energy of binding each substrate. Changing to the outward from the inward-facing conformation causes a shift in <scene name='69/694233/Transmembrane_helix_5/2'>TM5</scene> which disrupts the tetrahedral geometry of active site A. This in turn decreases binding affinity site A has for Zn²⁺ making export to the periplasm possible. After Zn²⁺ is exported and site A is either empty or bound to H⁺, the protein's conformation changes to the favored inward-facing conformation.

In contrast the main purpose of conformation change in the CTD is to stabilize the YiiP dimer and to act as a Zn²⁺ sensor.  

This is possible because of the flexible loop that links the TMD and the CTD. This loop harbors the <scene name='75/756372/Bestsaltbridgetransparent/1'>salt bridge</scene> which serves as a hinge that allows movement of the CTD. Using [https://en.wikipedia.org/wiki/F%C3%B6rster_resonance_energy_transfer FRET] to measure the distance between the CTD of each monomer fluorescence quenching was observed as the concentration Zn²⁺ increased, which supports that idea that Zn²⁺ induces a stabilizing conformation change in the CTD.<ref>PMID:19749753</ref> CTD of both monomers were measured to be closer together when saturated with Zn²⁺.