Bovine Plasma Kininogens<subtitle>III. Structural Comparison of High Molecular Weight and Low Molecular Weight Kininogens</subtitle>

Abstract

A method was developed for the purification of low molecular weight (LMW) kininogen from the same batch of bovine fresh plasma used for the isolation of high molecular weight (HMW) kininogen. Purified HMW kininogen reacted with both HMW and LMW kininogen antisera prepared, respectively, from immunized rabbit serum. Purified LMW kininogen also reacted with both antisera. Thus, the immunological properties of HMW and LMW kininogens were very similar, and their antigenic determinant groups seem to be identical. On treatment of purified HMW kininogen with cyanogen bromide, a fragment was obtained containing a kinin peptide sequence, from which kallidin was liberated by trypsin [EC 3.4.21.4]. The amino acid sequence of this fragment was identical to that of a fragment previously obtained from purified LMW kininogen by cyanogen bromide treatment. Moreover, tryptic peptide maps of S-carboxymethylated derivatives of HMW and LMW kininogens were very similar: the former gave 43 peptide spots and the latter 30 peptide spots; 28 peptide spots were found to be common to both kininogens. Thus, HMW kininogen seems to contain all the structural segments constituting LMW kininogen, though more detailed studies on the primary structures of the two are required to confirm this. The physicochemical and chemical properties of HMW and LMW kininogens were compared and differences were discussed.