The pH of calcium ions controls ion channel opening
(PHYSorg.com Chemistry)

Ion channels are pores in the membrane of cells or cell organelles. They allow positively or negatively charged particles, so-called ions, to be transported across the membrane. Biochemists at Johannes Gutenberg University Mainz (JGU) have now succeeded in imaging an important regulatory region of the human TRPML2 calcium ion channel at high resolution, an area of the channel shaped like a large ring on one side of the membrane. This ring acts like a doorman, deciding whether ions can move through the channel. `Our study has revealed the structure of the ring, which is also called the extracytosolic/lumenal domain (ELD), in human TRPML2 channels, and also that it is this domain that is responsible for the channel`s interaction with calcium,` said Professor Ute Hellmich of the JGU Institute of Pharmacy and Biochemistry-Therapeutical Life Sciences. Depending on the pH value, the calcium ions can open or block the channel, and therefore control their transport across cellular membranes.