Further purification and partial characterization of the rat lung cytoplasmic factors modulating adenylate cyclase activity in plasma membrane.

The adult rat lung cytoplasm contains some factors which markedly stimulate adenylate cyclase activity in plasma membranes (Nijjar, M.S. Biochim. Biophys. Acta 584:43-50, 1979). Adenylate cyclase activator (ACA) was purified from rat lungs by DEAE-cellulose chromatography, preparative isoelectric focusing and by repeated high-performance liquid chromatography on a Sepharogel TSK 2000SW column. The final preparation showed about 200 fold purification in ACA activity over the original lung supernatant, and appeared to be homogeneous on the basis of its migration into a single band on SDS-polyacrylamide gel electrophoresis, and co-elution of ACA activity with protein from a gel exclusion column. ACA is an acidic (pI 4.8 +/- 0.1), heat labile, monomeric protein of 40,000 +/- 2,000 dalton molecular weight, and does not resemble calmodulin.