Jy. Hwang et al., Calcium-dependent cysteine reactivities in the neuronal calcium sensor guanylate cyclase-activating protein 1, FEBS LETTER, 508(3), 2001, pp. 355-359
Guanylate cyclase-activating protein 1 (GCAP-1) is a Ca2+-sensing protein i
n vertebrate photoreceptor cells. It activates a membrane-bound guanylate c
yclase. Three of four cysteines present in wild-type GCAP-1 were accessible
to the thiol-modifying reagent 5,5'-dithio-bis-(2-nitrobenzoic acid) in th
e presence of Ca2+. Only Cys106 became exposed to the solvent after Ca2+-ch
elation. Since Cys106 is located in EF-hand 3, we could determine an appare
nt K-D of 2.9 muM for Ca2+ binding to this site with a fast off-rate (t sim
ilar to2 ms). We conclude that the rapid dissociation of Ca2+ from EF-hand
3 in GCAP-1 triggers activation of guanylate cyclase in rod cells. (C) 2001
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