Relation between number of apolipoprotein(a) kringle 4 repeats and mobility of isoforms in agarose gel: basis for a standardized isoform nomenclature.

The size of apolipoprotein(a) [apo(a)] varies from 187 to 648 kDa because of interallelic differences in the number of kringle 4-encoding sequences in the apo(a) gene. Plasma apo(a) isoform sizes were determined by a high-resolution sodium dodecyl sulfate-agarose gel electrophoretic method, followed by immunoblotting. The relation between the number of apo(a) kringle 4-encoding sequences in the apo(a) gene, as assessed by pulsed-field gel electrophoresis and genomic blotting, and the mobility of apo(a) isoforms in agarose gel was evaluated in 29 individuals who had 48 expressed apo(a) isoforms that contained between 12 and 41 kringle 4 repeats. The log of the kringle number was linearly related to the distance the isoform migrated on the agarose gel (r= 0.999). A nomenclature is proposed to designate apo(a) isoforms by the respective number of kringle 4 repeats.