H. Elhousni et al., PRODUCTION OF DOG CALCYPHOSINE IN BACTERIA AND LACK OF PHOSPHORYLATION BY THE CATALYTIC SUBUNIT OF PROTEIN-KINASE-A IN-VITRO, Molecular and cellular endocrinology, 135(1), 1997, pp. 93-97
Calcyphosine is a calcium-binding protein containing four EF-hand doma
ins that is found in several epithelia and in some cells of the centra
l nervous system. In thyroid follicular cells, calcyphosine is synthes
ized and phosphorylated in response to stimulation by thyrotropin and
cAMP agonists. The cDNA coding for dog calcyphosine has been expressed
in bacteria under the control of the T7 promoter. Recombinant calcyph
osine was purified from crude bacterial lysates by a combination of an
ion-exchange and hydrophobic interaction chromatography. Phosphorylati
on assays using the purified catalytic subunit of protein kinase A and
the recombinant or the native calcyphosine revealed that, contrary to
a previous report, calcyphosine is not significantly phosphorylated b
y this enzyme in vitro. (C) 1997 Elsevier Science Ireland Ltd.