Detection and identification of constitutive polypeptides of the third component of cornplement using microscale two-dimensional electrophoresis. Correlated with the separation by non-denaturing microscale two-dimensional electrophoresis.

Abstract

We have reported that the third component of complement (C3) is observed in the pattern of microscale non-denaturing two-dimensional electrophoresis (2-DE) after removal of IgG and IgA using protein A agarose and antibodies.1) For the investigation of constitutive polypeptides of the C3, the constituent polypeptides of human plasma proteins were analyzed using non-denaturing isoelectric focusing (IEF) in the first dimension and treated with mercaptoethanol/SDS, and then subjected to the second dimensional SDS electrophoresis (non-denaturing IEF/reduced-SDS PAGE). The α chain of C3 spot was detected in the pattern of non-denaturing IEF/reduced-SDS PAGE, but, the β chain of C3 spot was hidden by albumin spot. After albumin was removed using polyethylene glycol, both C3α and C3β spots were observed in the pattern of the non-denaturing IEF/reduced-SDS PAGE. The combining analysis of C3 in the non-denaturing 2-DE and the constituent polypeptides in the non-denaturing IEF/reduced-SDS PAGE can be useful for the analysis of C3 and its fragments during the activation of complements.