A new low-Ca2+ affinity GAP indicator to monitor high Ca2+ in organelles by luminescence

- We describe a novel low-affinity Ca2+ indicator based on the luminescent aequorin.
- The new biosensor is optimized for long-term recordings of high [Ca2+].
- The probe allows accurate measurements in organelles such as ER or Golgi.
- This new tool is applicable to quantitative bioluminescent high-throughput assays.