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Updated: Aug 9, 2026

Targeting Cysteine Thiols for in Vitro Site-specific Glycosylation of Recombinant Proteins
Published on: October 4, 2017
Calcium-dependent cysteine reactivities in the neuronal calcium sensor guanylate cyclase-activating protein 1
J Y Hwang1, R Schlesinger, K W Koch
1Institut für Biologische Informationsverarbeitung, Forschungzentrum Jülich, Germany.
Abstract:
Guanylate cyclase-activating protein 1 (GCAP-1) is a Ca(2+)-sensing protein in vertebrate photoreceptor cells. It activates a membrane-bound guanylate cyclase. 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 the presence of Ca(2+). Only Cys106 became exposed to the solvent after Ca(2+)-chelation. Since Cys106 is located in EF-hand 3, we could determine an apparent K(D) of 2.9 microM for Ca(2+) binding to this site with a fast off-rate (t approximately 2 ms). We conclude that the rapid dissociation of Ca(2+) from EF-hand 3 in GCAP-1 triggers activation of guanylate cyclase in rod cells.
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