L1, a major granulocyte protein: antigenic properties of its subunits.

L1, a major granulocyte protein, was purified and analysed by use of two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). Three subunits were visualized, and they were found to have molecular weights of 12.5 kDa, 13.3 kDa and 8.3 kDa. They were extracted from 2D-gels, and different combinations of subunits and two L1 antisera were analysed by immunodiffusion in agarose gel. The 8.3 kDa polypeptide in combination with one or both of the other polypeptides, gave immunoprecipitation with one of the L1 antisera, while no precipitation occurred when the three polypeptides were tested separately. Neither was there any precipitation when the two heavier polypeptides were tested in combination. By use of another L1 antiserum, all the L1 polypeptides were found to be antigenic and give immunoprecipitations. The L1 protein has a great affinity for calcium, and calcium was necessary for immunoprecipitation with the L1 subunits to occur. Autoradiographs of 2D-PAGE gels with labelled leucocytes visualized the L1 subunits in the same position as the subunits from purified, cold L1, indicating no significant alteration of the L1 protein during the purification procedure.