A SIMPLE METHOD FOR THE PREPARATION AND PURIFICATION OF C1 COMPLEMENTCLEAVED BETA(2)-MICROGLOBULIN FROM HUMAN SERUM

A simple method is described for the preparation of proteolytically pr ocessed forms of beta(2)-microglobulin suitable for structural and bio logical studies. PEG 6000 was added to the serum of healthy individual s to precipitate the Cl complement complex from Cl esterase inhibitor (Cl-inh). After dissolving the precipitate containing the Cl complemen t in Tris-HCl buffer, pH 7.6, efficient conversion of added beta(2)-mi croglobulin to desLys(58)beta(2)-microglobulin was observed. Addition of a specific carboxypeptidase B inhibitor (Plummers inhibitor) could partly prevent the deletion of Lys-58 from cleaved beta 2-microglobuli n, whereby Lys(58)-cleaved beta(2)-microglobulin was obtained. The pro teolytically processed forms were subsequently purified by G-75 Sephad ex gel filtration followed by chromatofocusing. A yield of 10-40% of p roteolytically processed beta(2)-microglobulin was obtained. Only one component was seen by SDS-PAGE stained with Coomassie Brilliant Blue.