Abstract
Trichoplusia ni granulosis virus granulin consists of one major polypeptide component with an estimated molecular weight of 28,000. The protein is phenol soluble, phosphorylated, and acidic. A protease activated by alkaline conditions is also associated with solubilized granulin preparations. If not properly inactivated, the protease will introduce extensive artifact into the protein giving rise to ambiguous and incorrect results as analyzed by SDS-polyacrylamide gel electrophoresis and peptide mapping. Procedures are documented for enzyme inactivation and the preparation of granulin in highly purified form for characterization.