Researchers at the Paul Scherrer Institute (PSI) have made significant advancements in understanding the interaction between calmodulin, a calcium-sensing protein, and an ion channel in the rod cells of the eye. These findings, published in PNAS, reveal the three-dimensional structure of the rod cyclic nucleotide-gated (CNG) ion channel as it binds calmodulin, a puzzle unresolved for three decades. This interaction is vital for the eye’s exceptional sensitivity to low light, enabling us to detect dim light conditions, such as starlight on clear nights. The ion channel closes in response to bright light, halting calcium ion flow and transforming biochemical signals into electrical ones for nervous system processing.
The study utilized cryo-electron microscopy and mass spectrometry to study this interaction within a flexible region of the channel, which significantly complicated structural interpretation. Collaborations among PSI, ETH Zurich, and the University of Bonn facilitated breakthroughs in understanding how calmodulin modulates the ion channel’s activity. The research highlights the critical role of calmodulin throughout the body, linking its dysfunction to various health concerns, including cardiac issues. This work not only enhances our comprehension of visual processes but may also provide insights into broader biological implications of calmodulin-regulated ion channels.
