CALCYCLIN FROM MOUSE EHRLICH ASCITES TUMOR-CELLS AND RABBIT LUNG FORMNONCOVALENT DIMERS

Crosslinking treatments of fresh cytosol from mouse Ehrlich ascites tu mor (EAT) cells revealed the existence of calcyclin dimers which were sensitive to SDS, but not to reducing agents, which suggests the exist ence of non-covalent dimers. In stored EAT cell cytosol and preparatio ns of purified calcyclin dimers were also formed by S-S bridging (cova lent dimers). The S-S dimers did not bind to organomercurial Agarose a nd could be separated from reduced forms of calcyclin that bound to th e resin. Calcyclin eluted from the resin with DTT was a mixture of mon omers and non-covalent dimers as shown by crosslinking and subsequent immunoblotting. Calcyclin from rabbit lung, lacking a cysteine residue , could also be crosslinked as a dimer. It is suggested that the abili ty of calcyclin to form non-covalent dimers is of physiological signif icance.