Xenopus laevis 19S immunoglobulin. Ultrastructure and J chain isolation.

Electron microscopy examination of the 19S immunoglobulin of Xenopus laevis revealed a hexameric structure with a central core. The molecules measured 360-430 A across the span of the arms and the average diameter of the central region was 140 A. A polypeptide, homologous to human J chain, was isolated by chromatography on DEAE-cellulose from the reduced and alkylated X. laevis hexameric macroglobulin. This polypeptide had a fast mobility in alkaline-urea gel electrophoresis, with distinct antigenicity, as compared to heavy and light chains. It shared common antigenic determinants with human J chain.