Semi-synthetic aequorins with improved sensitivity to Ca2+ ions.
Thirty-seven coelenterazine analogues were synthesized and incorporated into apo-aequorin, yielding 30 semi-synthetic aequorins that have the capacity to emit a significant amount of light in the presence of Ca2+. The properties of resultant photoproteins were investigated. The most prominent feature of those photoproteins was the wide range in their sensitivities to Ca2+ concentration. The relative intensity of Ca2+-triggered luminescence of the photoproteins ranged from 0.01 to 190 when compared with natural aequorin (relative intensity 1.0) at pCa 6 for the cases where the relative intensity is less than 1 and at pCa 7 for the cases where the relative intensity is higher than 1. Eight of the semi-synthetic aequorins belonged to the class of e-aequorin. With two of those photoproteins, the degree of dependence of the luminescence intensity ratio I400/I465 on pCa was greater than that with e-aequorin, suggesting that these two photoproteins are possibly superior to e-aequorin in measuring Ca2+ concentration by the ratio method.
Shimomura
O
O
Marine Biological Laboratory, Woods Hole, MA 02543.
Musicki
B
B
Kishi
Y
Y
D000331:Aequorin / Q000031:analogs & derivatives; D000818:Animals; D002118:Calcium; D008163:Luminescent Measurements; D008164:Luminescent Proteins
D008164:Luminescent Proteins; D000331:Aequorin; D002118:Calcium