P-30, A NOVEL PROTEIN TARGET OF MOUSE CALCYCLIN (S100A6)

A novel protein target of mouse calcyclin (S100A6) was detected by a g el overlay method with I-125-labelled calcyclin. Interaction of calcyc lin with its 30 kDa target protein (p30) present in Ehrlich ascites tu mour (EAT) cells depended on the presence of Ca2+ ions. The binding of p30, evidenced by the reaction with (12)5I-labelled calcyclin, was fo und to be of higher affinity than the binding between mouse calcyclin and annexin II or glyceraldehyde-3-phosphate dehydrogenase. Examinatio n of tissue extracts by the gel overlay method has shown that p30 is p resent not only in the EAT cells but also in mouse brain and spleen. T his novel target protein of mouse calcyclin was purified to homogeneit y from EAT cells by means of Phenyl-Sepharose chromatography, affinity chromatography and CM-cellulose chromatography. Purified p30 was dige sted with alpha-chymotrypsin and a partial amino acid sequence of one of the resulting peptides was established. A database search analysis revealed that the sequence is unique, with a similarity of less than 5 5% to. any other known protein sequence.