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.