Purification of maize cytosolic 70 kD stress protein: A calmodulin-binding protein in plants

The maize cytosolic 70 kD stress protein (HSC70) has been purified by a two-step procedure employing affinity chromatography on ATP-agarose followed by DEAF52 ion-exchange chromatography. Using a biotinylated cauliflower calmodulin (CaM) gel-overlay technique in the presence of 1 mmoL/L Ca2+, the HSC70 could bind to CaM. No band was shown on sodium dodecyl sulfate-polyacrylamide gel overlayed with biotinylated cauliflower CaM when 1 mmol/L Ca2+ was replaced by 5 mmol/L EGTA. It indicated that the binding of HSC70 to CaM was dependent on Ca2+. The purified HSC70 inhibited the activity of CaM-dependent NADK and the degree of inhibition increased with augmentation of the HSC70, which appeared to be typically characteristic to CaM-binding protein.