Calcium influx through annexin V ion channels into large unilamellar vesicles measured with fura-2.

A new assay for the calcium channel activity of annexin V was developed. The calcium-sensitive fluorescence indicator, fura-2, was incorporated into large unilamellar vesicles (LUV). After establishing a calcium gradient across the liposomal membranes, native or mutated annexin V was added. The resulting calcium influx into the LUV detected through the fluorescence changes of fura-2 was used as a qualitative test for the electrophysiological properties of annexin V.