RAPID PURIFICATION AND IDENTIFICATION OF CALCYPHOSINE, A CA2-BINDING PROTEIN PHOSPHORYLATED BY PROTEIN KINASE-A()

A method is presented for the rapid purification of dog thyroid calcyp hosine, a protein previously identified as a major substrate for cycli c AMP-dependent protein kinase in dog thyroid slices stimulated by thy rotropin [Lecocq, Lamy and Dumont (1979) Eur. J Biochem 102, 147-152]. The protein was previously identified as a spot on two-dimensional ge ls and is now purified in its native form by a procedure involving thr ee chromatographic steps. Homogeneous calcyphosine identified by SDS/P AGE, immunoblotting and peptide sequencing can be obtained within 7 h. As for calmodulin, Ca2+-dependent conformational changes can be shown by Ca2+-dependent hydrophobic interaction chromatography using phenyl -Sepharose. Unlike calmodulin, calcyphosine is a substrate for protein kinase A.