schematic of zinc transporter mechanism (IMAGE) DOE/Brookhaven National Laboratory Caption Schematic of the mechanism for the transmembrane ZIP transporter (blue, orange, and green—with gray bars representing part of the other half of the two-molecule dimer). a) When zinc (red) inside the cell (cytoplasm) is low, the part of the protein facing the environment (periplasm) is open so zinc can enter a pore in the protein. b) The blue portion of the protein moves up slightly and tilts to transport zinc into the cell. c) When zinc inside the cell gets too high, it binds to the flexible green loop, which then folds back and binds to sites inside the pore to block the exit of zinc. When zinc levels inside the cell fall, the loop will pop back out to allow zinc to enter again. Credit Brookhaven National Laboratory Usage Restrictions OK for use in stories about this research License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.