Ultrastructure of hepatitis B virus surface antigen produced by transformed yeast: analysis with negative staining and ice embedding

Abstract

Ultrastructure of hepatitis B virus surface antigen(HBsAg)produced by transformed yeast was analyzed with high-resolution negative staining and ice embedding. By negative staining, HBsAgs produced by yeast were either spherical, or slightly elongated. Their mean diameter and length were27.5nm and32.5nm respectively. They were angular in outline, and consisted of many subunits whose diameter was about4.3nm. Each subunit had a hollow. Thus, it became apparent that yeast HBsAg was bigger(about27.5nm)than HBsAg derived from human plasma(about21nm). Also, yeast HBsAg showed hollow-subunit structure about4.3nm in diameter, whereas human HBsAg showed knob-like subunits about3nm in diameter. These morphological differences between yeast and human HBsAg may be attributable to that the yeast HBsAg is mainly composed of disulfide-bonded dimers of polypeptides lacking glycosylated side-chains, whereas the human HBsAg is composed of polypeptides with or without glycosylated side-chains.By ice embedding, where specimens are hydrated and unfixed, yeast HBsAgs were either spherical, or slightly elongated, and had electron-lucent centers. They were smooth in outline, and had jelly-like appearances. Their mean diameter and length were 23.7nm and27.0nm respectively. The apparent bigger size of negatively stained yeast HBsAg may have been caused by flattening due to surface tension when they were dried in air; the size measured by ice-embedding may give a true value.